Hydraulic braking pressure control unit

ABSTRACT

A hydraulic braking pressure control unit including three or more hydraulic pressure control components, and a holder structure which holds those hydraulic pressure control components, wherein the three or more hydraulic pressure control components are selected from electromagnetically operated hydraulic pressure control valves capable of controlling a pressure of a working fluid in a brake cylinder in a braking system, and pressure detecting devices, to detect respective pressures of the fluid used to control the electromagnetically operated hydraulic pressure control valves. The three or more hydraulic pressure control components include three hydraulic pressure control components which are attached to the holder structure such that one of the three hydraulic pressure control components is spaced from the other two hydraulic pressure control components by substantially the same distance.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of application Ser. No.10/117,035, filed Apr. 8, 2002, which is based on Japanese PatentApplications Nos. 2001-117913, filed on Apr. 17, 2001, and 2001-156449,filed May 25, 2001. The disclosures of the priority applications arehereby incorporated by reference herein.

BACKGROUND

The present invention relates to a hydraulic braking pressure controlunit.

There is known a hydraulic braking pressure control unit which includesa plurality of electromagnetically operated hydraulic pressure controlvalves capable of controlling brake cylinders, and hydraulic pressuredetecting devices. The hydraulic pressure control valves and thehydraulic pressure detecting devices are held by a holder structure.

U.S. Pat. No. 5,577,813 (corresponding to JP-A-8-502007) discloses anexample of such a hydraulic braking pressure control unit, whichincludes: (i) a power operated hydraulic pressure source having (a) apump device including a pump arranged to pressurize a working fluidreceived from a low pressure source and deliver the pressurized workingfluid, and a motor operable to drive the pump, and (b) an accumulatorarranged to store the working fluid delivered from the pump device, (ii)a control valve device including at least one control valve each capableof controlling a hydraulic braking pressure in a brake cylinder foroperating a brake, by utilizing the fluid delivered from the poweroperated hydraulic pressure source, and (iii) a holder structure whichhas a first surface and a second surface opposite to each other, and athird surface adjacent to the first and second surfaces. The holderstructure include first, second and third portions respectively havingthe first, second and third surfaces. The holder structure holds thepower operated hydraulic pressure source and the control valve devicesuch that each of the above-indicated at least one control valve isattached at its main body portion to the first portion, and the motor isattached at its main body portion to the second portion, while theaccumulator is attached at its main body portion to the third portion.

SUMMARY

It is an object of the present invention to provide a hydraulic brakingpressure control unit which is arranged to be relatively small-sized.This object may be achieved according to any one of the following modesof the present invention in the form of a hydraulic braking pressurecontrol unit, each of which is numbered like the appended claims anddepends from the other mode or modes, where appropriate, to indicate andclarify possible combinations of elements or technical features. It isto be understood that the present invention is not limited to thetechnical features or any combinations thereof which will be describedfor illustrative purpose only. It is to be further understood that aplurality of elements or features included in any one of the followingmodes of the invention are not necessarily provided all together, andthat the invention may be embodied without some of the elements orfeatures described with respect to the same mode.

(1) A hydraulic braking pressure control unit comprising:

-   -   at least three hydraulic pressure control components selected        from (i) electromagnetically operated hydraulic pressure control        valves capable of controlling a pressure of a working fluid in a        brake cylinder in a braking system, and (ii) pressure detecting        devices used to detect respective pressures of the fluid, to        control the electromagnetically operated hydraulic pressure        control valves; and    -   a holder structure which holds the at least three hydraulic        pressure control components,    -   and wherein the at least three hydraulic pressure control        components include three hydraulic pressure control components        which are attached to the holder structure such that one of the        three hydraulic pressure control components is spaced from the        other two of the three hydraulic pressure control components by        a substantially same distance.

In the hydraulic braking pressure control unit constructed according tothe above mode (1) of the present invention, the three hydraulicpressure control components are located at respective three apexes of anisosceles triangle. In other words, one of the three components islocated on a straight line which is normal to a segment connecting thecenters of the other two components and which passes a midpoint of thatsegment. Where the hydraulic braking pressure control units include arelatively large number of hydraulic pressure control components thatinclude two or more sets of three components wherein the threecomponents of each set are positioned relative to each other asdescribed above, the components are arranged in a zigzag or staggeredpattern on the holder structure, so that the number of the componentsthat can be attached per unit surface area of the holder structure canbe made larger, than where the components are arranged in a rectangularlattice pattern. Accordingly, the present arrangement permits anincreased density of arrangement of the hydraulic pressure controlcomponents, and effective utilization of the surface area of the holderstructure, thereby making it possible to reduce the required size of thehydraulic braking pressure control unit. Thus, the present arrangementis advantageous where the unit includes a relatively large number ofhydraulic pressure control components.

The three hydraulic pressure control components located at therespective apexes of an isosceles triangle may be of the same kind, orone of the three components is different in kind from the other twocomponents. For instance, the three components are allelectromagnetically operated hydraulic pressure control valves, orpressure detecting devices. Alternatively the two components areelectromagnetically operated hydraulic pressure control components whilethe third component is a pressure detecting device, or the twocomponents are pressure detecting devices while the third component is ahydraulic pressure control valve. Described more specifically, apressure detecting device may be spaced from two hydraulic pressurecontrol valves by the same distance, or a hydraulic pressure controlvalve may be spaced from two pressure detecting devices by the samedistance. Further alternatively, either a hydraulic pressure controlvalve or a pressure detecting device may be spaced from a hydraulicpressure control valve and a pressure detecting device by the samedistance.

Each pressure detecting devices is provided to detect a pressure of thefluid, which pressure is used to control the electromagneticallyoperated hydraulic pressure control valves. For instance, the pressuredetecting device may be a brake cylinder pressure detecting device usedto detect the hydraulic braking pressure in the brake cylinder, a poweroperated pressure source pressure detecting device used to detect thepressure of a pressurized fluid delivered from a power operatedhydraulic pressure source, or a master cylinder pressure detectingdevice used to detect the pressure of a pressurized fluid delivered froma master cylinder. Where the hydraulic braking pressure in the brakecylinder is controlled on the basis of the pressure of the pressurizedfluid delivered from the power operated hydraulic pressure source, theelectromagnetically operated hydraulic pressure control device iscontrolled on the basis of the pressure of the pressurized fluidreceived from the power operated hydraulic pressure source. Where thehydraulic braking pressure in the brake cylinder is controlled so as tobe equal to a target or desired value determined on the basis of thepressure of the pressurized fluid delivered from the master cylinder,the hydraulic pressure control valve is controlled on the basis of thefluid pressure of the master cylinder.

The electromagnetically operated hydraulic pressure control valves mayinclude not only control valves arranged to directly increase or reducethe hydraulic braking pressure in the brake cylinder, but alsoelectromagnetically operated valves arranged to isolate the brakecylinder from the master cylinder when the hydraulic braking pressure inthe brake cylinder is controlled by utilizing the pressurized fluiddelivered from the power operated hydraulic pressure source.

The principle of the present invention according to the above mode (1)requires at least three hydraulic pressure control components of thehydraulic braking pressure control unit to include three components thatare attached to the holder structure such that these three componentsare positioned relative to each other as described above. However, theprinciple of the present invention does not require all of the hydraulicpressure control components of the unit to satisfy the positionalrelationship as described above.

The hydraulic braking pressure control unit according to the above mode(1) may include the technical feature according to any one of thefollowing modes (28), (32), (33), (36), (38), (40) and (41).

(2) A hydraulic braking pressure control unit according to the abovemode (1), wherein the holder structure includes a portion having onesurface, and the above-indicated at least three hydraulic pressurecontrol components are attached to the holder structure such that a mainbody portion of each of the at least three hydraulic pressure controlcomponents is fixed to the above-indicated portion of the holderstructure.

In the braking hydraulic pressure control unit according to the abovemode (2), each hydraulic pressure control component is fixed to aportion of the holder structure on the side of one surface of the holderstructure, so that the signal wires or lines connected to the componentscan be relatively easily bundled together.

Where the component is at its main body portion fixed to a portion ofthe holder structure o the side of one surface of the holder structure,it is common that a part of the main body portion is received in arecess open in that one surface of the holder structure while the otherpart of the main body portion projects from the surface. The partreceived in the recess may be larger than the other part projecting fromthe surface, or vice versa. In either case, the recess may function as aportion of the electromagnetically operated hydraulic pressure controlvalve or pressure detecting device. Where the recess formed in theholder structure functions as a portion of the electromagneticallyoperated hydraulic pressure control valve, for example, the hydraulicpressure control valve is constituted by a part of the holder structuredefining the recess, and the main body portion fixed to the holderstructure. Where the recess of the holder structure does not function asa portion of the electromagnetically operated hydraulic pressure controlvalve, that is, where the main body portion is capable of functioning asthe hydraulic pressure control valve before the main body portion isfixed to the holder structure, only the main body portion is consideredto function as the hydraulic pressure control valve. Where the recess ofthe holder structure function as a portion of the hydraulic pressurecontrol valve, the recess may partially define a fluid chamber orcommunication passage that is required to be formed in the hydraulicpressure control valve.

(3) A hydraulic braking pressure control unit according to the abovemode (1) or (2), wherein the above-indicated at least three hydraulicpressure control components include two components which are arrangedalong a reference line, and another component which is spaced from thereference line in a direction perpendicular to the reference line.

The reference line may be parallel to an X-axis or Y-axis direction of asurface of the holder structure (a direction of short or long sides of arectangular surface of the holder structure, or a longitudinal ortransverse direction of the rectangular surface). Where the two or morehydraulic pressure control components are arranged along the referenceline while another hydraulic pressure component is located at a distancefrom the reference line, the surface area available on the holderstructure can be effectively utilized for attachment of the components,with a reduced wasting of the surface area, if the above-indictedanother component is spaced from the adjacent two components by the samedistance. This arrangement permits significant reduction of the requiredsize of the braking hydraulic pressure control unit.

(4) A hydraulic braking pressure control unit comprising (a) a pluralityof electromagnetically operated hydraulic pressure control valvescapable of controlling a pressure of a working fluid in a brakecylinder, and (b) a holder structure which holds the plurality ofelectromagnetically operated hydraulic pressure control valves, andwherein the plurality of electromagnetically hydraulic pressure controlvalves have respective main body portions which are arranged along astraight line on one surface of the holder structure, and the holderstructure has at least one fluid passage which is formed in the holderstructure such that each fluid passage extends in a directionintersecting the straight line, between two adjacent ones of theelectromagnetically operated hydraulic pressure control valves as seenin a plane of the above-indicated one surface.

In the hydraulic braking pressure control unit according to the abovemode (4) of this invention, each fluid passage is formed in the holderstructure, by utilizing portions of the holder structure not occupied bythe hydraulic pressure control valves, so that the required size of thehydraulic braking pressure control unit can be reduced. Theabove-indicated at least one fluid passage may include a high pressurepassage connected to a high pressure source, and a low pressure passageconnected to a low pressure source.

The hydraulic braking pressure control unit according to the above mode(4) may include the technical feature according to any one of the abovemodes (1)-(3). For instance, pressure detecting devices as well as thehydraulic pressure control valves may be arranged along the straightline. The fluid passage or passages may be formed according to the abovemode (4), in the holder structure of the hydraulic braking pressurecontrol unit according to any one of the above modes (1)-(3).

Further, the hydraulic braking pressure control unit according to theabove mode (4) may include the technical feature according to any one ofthe following modes (28), (32), (33), (36), (38), (40) and (41).

(5) A hydraulic braking pressure control unit according to the abovemode (4), wherein the above-indicated at least one fluid passageincludes at least one high pressure passage connected to a high pressuresource.

(6) A hydraulic braking pressure control unit according to the abovemode (4) or (5), wherein the above-indicted at least one fluid passageincludes at least one passage formed so as to extend in a directionsubstantially perpendicular to the straight line as seen in said plane.

Where the at least one fluid passage is formed so as to extendsubstantially perpendicularly to the straight line, the fluid passage orpassages may be effectively formed in the holder structure, withoutincreasing the size of the holder structure.

(7) A hydraulic braking pressure control unit according to any one ofthe above modes (4)-(6), wherein the above-indicated at least one fluidpassage includes at least one passage formed so as to extend along astraight line which is normal to a segment connecting the centers of theadjacent ones of the plurality of electromagnetically operated hydraulicpressure control valves and which passes a midpoint of the segment, asseen in the plane of the above-indicated one surface.

(8) A hydraulic braking pressure control unit according to any one ofthe above modes (5)-(7), wherein the plurality of electromagneticallyoperated hydraulic pressure control valves whose main body portions arearranged along the straight line consist of four control valves, and thehigh pressure source includes a power operated hydraulic pressure sourcepower-operable to pressurize the working fluid, and a master cylinderoperable by an operator by the unit, the above-indicated at least onefluid passage including a pressure source passage connected to the poweroperated hydraulic pressure source, and at least one master cylinderpassage connected to the master cylinder, each of the pressure sourcepassage and the maser-cylinder passage being formed in the holderstructure, so as to extend in the direction intersecting the straightline, between adjacent ones of the four control valves, as seen in theabove-indicated plane.

In the hydraulic braking pressure control unit according to the abovemode (8), one pressure source passage and two master cylinder passagesmay be formed between respective three pairs of adjacent control valvesof the four control valves, for example.

(9) A hydraulic braking pressure control unit according to any one ofthe above modes (4)-(8), which is used for a braking system having twomutually independent sub-systems.

Where the braking system is used for an automotive vehicle, the brakingsystem may be of an independent front-rear piping arrangement or anindependent X-crossing piping arrangement. Namely, the two mutuallyindependent sub-systems may consist of a front-wheel braking sub-systemfor braking the vehicle front wheels and a rear-wheel braking sub-systemfor braking the vehicle rear wheels, or alternatively, a first diagonalbraking sub-system for braking the front left wheel and the rear rightwheel, and a second diagonal braking sub-system for braking the frontright wheel and the rear left wheel.

The technical feature according to the above mode (9) is applicable tothe hydraulic braking pressure control unit according to any one of theabove modes (1)-(3).

(10) A hydraulic braking pressure control unit according to the abovemode (9), wherein the plurality of electromagnetically operatedhydraulic pressure control valves consist of four control valvesconsisting of a first pair of control valves which are included in oneof the two mutually independent sub-systems and which are arrangedadjacent to each other, and a second pair of control valves which areincluded in the other of the two mutually independent sub-systems andwhich are arranged adjacent to each other such that one of the secondpair of control valves is adjacent to one of the first pair of controlvalves.

The technical feature according to the above mode (10) is applicable toa hydraulic braking pressure control unit in which a plurality ofpressure detecting devices, rather than the electromagnetically operatedhydraulic pressure control valves, are arranged as hydraulic pressurecontrol components, along a straight line on one surface of the holderstructure.

(11) A hydraulic braking pressure control unit according to the abovemode (9) or (10), wherein the four control valves consist of a firstpair of control valves and a second pair of control valves which aredisposed on respective opposite sides of a straight line which is normalto a segment connecting centers of inner two control valves of the fourcontrol valves and which passes a midpoint of the segment, as seen in aplane of the above-indicated one surface of the holder structure, thefirst and second pairs of control valves being respectively included thetwo mutually independent sub-systems.

(12) A hydraulic braking pressure control unit according to any one ofthe above modes (9)-(11), wherein the above-indicated one surface of theholder structure is bisected into two areas by a bisector line which isperpendicular to the straight line, the electromagnetically operatedhydraulic pressure control valves consisting of a first group of controlvalves and a second group of control valves which are respectivelyincluded in the two mutually independent sub-systems.

(13) A hydraulic braking pressure control unit according to any one ofthe above modes (9)-(12), wherein the holder structure consists of twohalves which are located on respective opposite sides of a bisectorplane which includes a bisector line perpendicular to the straight lineand which is perpendicular to the above-indicated one surface, thebisector line being located at a substantially central position on theabove-indicated one surface as seen in a direction of the straight line,the holder structure having at least one first fluid passage and atleast one second fluid passage which are respectively formed in the twohalves of the holder structure.

Each fluid passage is preferably formed so as to extend in a directionparallel to or perpendicular to the bisector line.

(14) A hydraulic braking pressure control unit according to any one ofthe above modes (8)-(13), wherein the pressure source passage is formedbetween two inner control valves of the four control valves, as seen inthe above-indicated plane.

Where the four control valves consist of two pairs of control valveswhich are included in the respective two mutually independentsub-systems, the pressurized fluid delivered from the power operatedhydraulic pressure source can be equally utilized by the twosub-systems, where the pressure source passage is formed between the twopairs of control valves. The pressure source passage may be formed so asto extend along the bisector line, as seen in the plane of theabove-indicated one surface of the holder surface.

(15) A hydraulic braking pressure control unit according to any one ofthe above modes (8)-(14), wherein the above-indicated at least onemaster cylinder passage consists of two master cylinder passages each ofwhich is formed so as to extend between two adjacent ones of theelectromagnetically operated hydraulic pressure control valves, as seenin the plane, the adjacent ones being included in a corresponding one ofthe two mutually independent two sub-systems.

Where the master cylinder has two pressurizing chambers, the fluidpressurized in one of the two pressurizing chambers is supplied to oneof the two sub-systems, while the fluid pressurized in the otherpressurizing chamber is supplied to the other sub-system.

(16) A hydraulic braking pressure control unit according to any one ofthe above modes (8)-(15), wherein the plurality of electromagneticallyoperated pressure control valves includes a master cylinder cut-offvalve attached to the one surface, in communication with a portion ofeach of the at least one master cylinder passage, which portion islocated on one of opposite sides of the straight line, the mastercylinder cut-off valve being operable to selectively open and close theeach master cylinder passage, the unit further including a mastercylinder pressure detecting device attached to the one surface, incommunication with another portion of the each master cylinder passage,which another portion is located on the other of the opposite sides ofthe straight line, the master cylinder pressure detecting device beingoperable to detect a pressure of the working fluid in the each mastercylinder passage.

Where the holder structure holds the master cylinder cut-off valve andthe master cylinder pressure detecting device as well s the controlvalves, the function to be performed by the unit is improved. Further,where the master cylinder cut-off valve and the master cylinder pressuredetecting device are disposed on the respective opposite sides of theabove-indicated straight line, the required size of the unit can be madesmaller than where the cut-off valve and the pressure detecting deviceare disposed on one side of the straight line.

(17) A hydraulic braking pressure control unit according to the abovemode (16), wherein the portion of the each master cylinder passagelocated on the one of the opposite sides of the straight line isconnected to the master cylinder.

(18) A hydraulic braking pressure control unit according to any one ofthe above modes (4)-(17), wherein the holder structure has a pluralityof fluid passages formed in parallel to each other.

The fluid passages may include the above-indicated pressure sourcepassage and master cylinder passage or passages, and at least one brakecylinder passage connected to at least one brake cylinder. The parallelarrangement of these fluid passages permits effective utilization of thevolume of the holder structure. The fluid passages may have the samedepth or different depths from the above-indicated one surface of theholder structure. The volume of the holder structure can be utilizedmore effectively where the fluid passages are formed with differentdepth values. The fluid passages are preferably formed so as to extendin a direction perpendicular to the straight line along which thehydraulic pressure control valves are arranged.

(19) A hydraulic braking pressure control unit according to any one ofthe above modes (5)-(18), wherein the above-indicated at least one atleast one high pressure passage consists of a plurality of high pressurepassages, and the holder structure has four brake cylinder portsconnected to respective four brake cylinders, and a plurality of highpressure ports connected to the plurality of high pressure passages, thefour brake cylinder ports and the plurality of high pressure ports beingarranged in a zigzag pattern, along respective two straight lines whichare spaced apart from each other, such that the brake cylinder ports andthe high pressure ports are alternately arranged in a direction parallelto the two straight lines.

The brake cylinder ports and the high pressure ports may be formed in asurface of the holder structure which is perpendicular to the directionof extension of the fluid passages, for example. The brake cylinderports and high pressure ports are connected through joints to pipes,hoses or other connecting members, which are in turn connected to thebrake cylinders or the high pressure source. Accordingly, spaces forattachment and manipulation of the joints are required to be providedaround the ports. Where the brake cylinder ports and high pressure portsare all arranged along a single straight line, the surface of the holderstructure in which those ports are formed is required to have arelatively large length along the straight line. Where those ports arearranged along the respective two straight lines, in a zigzag orstaggered pattern, an increase of the required length of the surface canbe avoided. The zigzag arrangement of the brake cylinder ports and thehigh pressure ports requires that the fluid passages communicating withthe brake cylinder ports and the fluid passages communicating with thehigh pressure ports be formed at different positions in a directionperpendicular to the above-indicated one surface on which the hydraulicpressure control valves are arranged.

(20) A hydraulic braking pressure control unit according to any one ofthe above modes (1)-(19), wherein the holder structure includes aportion having one surface, and has a plurality of brake cylinderpassages formed for connection to respective brake cylinders, and atleast one connecting passage each formed for communication between twopassages of the plurality of brake cylinder passages, theelectromagnetically operated hydraulic pressure control valves includingat least one communication control valve attached to the above-indicatedportion of the holder structure, the above-indicated at least onecommunication control valve being provided for the at least oneconnecting passage and operable to selectively open and close acorresponding one of the at least one connecting passage.

Where the holder structure of the hydraulic braking pressure controlunit holds the communication control valve or valves, the function ofthe unit is accordingly improved. It is desirable to form the pluralityof brake cylinder passages in parallel with each other, and form eachconnecting passage so as to extend in a direction perpendicular to thebrake cylinder passages.

(21) A hydraulic braking pressure control unit including (a) a pressureincreasing control valve operable to increase a pressure of a workingfluid in a brake cylinder, by effecting communication of said brakecylinder with a high pressure source, (b) a pressure reducing controlvalve operable to reduce the pressure of the working fluid in the brakecylinder, by effecting communication of the brake cylinder with a lowpressure source, (c) a brake cylinder pressure detecting device operableto detect the pressure in the brake cylinder, and (d) a holder structurewhich holds the pressure increasing and pressure reducing control valvesand the brake cylinder pressure detecting device, and wherein the holderstructure includes a portion having one surface, and the pressureincreasing control valve, the pressure reducing control valve and thebrake cylinder pressure detecting device are attached to theabove-indicated portion of the holder structure such that the pressurereducing and pressure reducing control valves and the brake cylinderpressure detecting device are arranged along a substantially straightline on the above-indicated one surface, and such that the brakecylinder pressure detecting devices is located at a substantiallymidpoint between the pressure increasing and pressure reducing controlvalves.

Where the brake cylinder pressure detecting device is attached to theholder structure such that the brake cylinder pressure detecting deviceis located at a substantially midpoint between the pressure increasingand pressure reducing control valves, changes of the fluid pressure bythe operations of the pressure increasing and pressure reducing controlvalves can be equally detected by the pressure detecting device.Accordingly, this arrangement is effective to reduce inconsistencybetween the pressure increase control and the pressure decrease controlby those two control valves, making it possible to improve the accuracyof control of the hydraulic braking pressure in the brake cylinder.

Where the holder structure holds a plurality of sets of pressureincreasing and pressure reducing control valves and brake cylinderpressure detecting devices, it is desirable to arrange the controlvalves and pressure detecting devices such that a plurality of straightrows each consisting of the pressure increasing and pressure reducingcontrol valves and brake cylinder pressure detecting device are parallelto each other. That is, the two or more sets of control valves andpressure detecting devices are desirably arranged in a rectangularlattice pattern. Although the control valves and the pressure detectingdevices may be arranged in a zigzag or staggered pattern, pressureincreasing and pressure reducing brake cylinder passages may be moreconveniently formed commonly for the pressure increasing and pressurereducing control valves, where the control valves and pressure detectingdevices are arranged in the rectangular lattice pattern, than where theyare arranged in the zigzag pattern. This aspect will be described indetail in the DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS.

The hydraulic braking pressure control unit according to the above mode(21) may include the technical features according to any one of theabove modes (1)-(20). Where the unit according to the mode (21) includesthe technical feature according to the mode (4), for example, thestraight line described with respect to the mode (4) intersects thestraight line described with respect to the mode (21), preferably atright angles.

The hydraulic braking pressure control unit according to the above mode(21) may further include the technical feature according to any one ofthe following modes (28), (32), (33), (36), (38), (40) and (41).

(22) A hydraulic braking pressure control unit according to the abovemode (21), wherein the holder structure has a pressure increasing brakecylinder passage connecting the brake cylinder pressure detecting deviceand the pressure increasing control valve, and a pressure reducing brakecylinder passage connecting the brake cylinder pressure detecting deviceand the pressure reducing control valve, the pressure increasing brakecylinder passage and the pressure reducing brake cylinder passage beingformed at different positions in a direction perpendicular to theabove-indicated one surface of the holder structure.

Where the pressure increasing and pressure reducing control valves havethe same construction wherein the high pressure and low pressure portsof each of these control valves are formed at different positions in theaxial direction of the control valves, the positional relationship inthe above-indicated axial direction between the brake cylinder pressuredetecting device and the pressure increasing and pressure reducing brakecylinder passages is determined by the relationship among the pressureincreasing control valve, a high pressure port connected to a highpressure source and a brake cylinder passage connected to the brakecylinder, and the relationship among the pressure reducing controlvalve, the brake cylinder passage and a low pressure passage connectedto a reservoir. In the hydraulic braking pressure control unit accordingto the above mode (22), the pressure increasing and pressure reducingbrake cylinder passages are formed at different positions in the axialdirection of the brake cylinder pressure detecting device (axialdirection of the control valves).

Therefore, the arrangement according to the above mode (22) eliminates aneed of forming a fluid passage in the holder structure, so as to extendin the axial direction of the control valves, and consequently eliminatea need of closing the open ends of this fluid passage, so that the costof manufacture of the hydraulic braking pressure control unit can bereduced.

(23) A hydraulic braking pressure control unit according to the abovemode (21) or (22), wherein the holder structure holds at least twostraight arrays of pressure increasing control valves, pressure reducingcontrol valves and brake cylinder pressure detecting devices, which areattached to the above-indicated portion of the holder structure, theholder structure having at least two brake cylinder passages formed forcommunication with the pressure increasing and pressure reducing controlvalves and the brake cylinder pressure detecting device of theabove-indicated at least two straight arrays, respectively, said holderstructure further having a connecting passage formed for communicationbetween two passages of the at least two brake cylinder passages, thehydraulic braking pressure control unit further including acommunication control valve which is attached to the above-indicatedportion of the holder structure and which is operable to selectivelyopen and close the connecting passage.

(24) A hydraulic braking pressure control unit according to any one ofthe above modes (4)-(23), wherein the control valves includes at leastone group of control valves each consisting of a plurality ofelectromagnetically operated pressure control valves of the same kindwhich are arranged along a substantially straight line on theabove-indicated surface of the holder structure.

Where the two or more electromagnetically operated pressure controlvalves of the same kind (of the same size) are arranged along a straightline, the volume of the holder structure can be effectively utilized,making it possible to reduce the required size of the holder structureand the required size of the hydraulic braking pressure control unit.

The electromagnetically operated pressure control valves of the samekind can be usually connected to each other by a single fluid passage.In this case, the control valves are desirably arranged along a straightline. There are various kinds of electromagnetically operated pressurecontrol valves, such as a pressure increasing control valve, a pressurereducing control valve, a master cylinder cut-off valve and acommunication control valve

The technical feature according to the above mode (24) is applicable tothe hydraulic braking pressure control unit according to any one of theabove modes (1)-(3). In this case, the two or more hydraulic pressurecontrol components of the same kind are arranged along a straight line.for instance, the brake cylinder pressure detecting devices or themaster cylinder pressure detecting devices are arranged along a straightline. Further, two or more groups of the hydraulic pressure controlcomponents of different kinds may be arranged such that thecorresponding straight rows of the components of the different kinds areparallel to each other.

(25) A holder structure which holds at least three hydraulic pressurecontrol components, wherein the holder structure includes a portionhaving one surface, and the at least three hydraulic pressure controlcomponents are attached to the above-indicated portion of the holderstructure such that the hydraulic pressure control components arelocated at respect apexes of at least one isosceles triangle.

The holder structure according to the above mode (25) may include thetechnical feature according to any one of the above modes (1)-(24).

(26) A holder structure which holds a plurality of electromagneticallyoperated hydraulic pressure control valves such that the hydraulicpressure control valves are arranged along a straight line on onesurface of the holder structure, the holder structure having a pluralityof fluid passages each of which is formed so as to extend in a directionintersecting the straight line, between two adjacent ones of theplurality of electromagnetically operated hydraulic pressure controlvalves, as seen in a plane of the above-indicated one surface.

The holder structure according to the above modes (26) may include thetechnical feature according to any one of the above modes (1)-(24).

(27) A hydraulic braking pressure control unit comprising:

-   -   a power operated hydraulic pressure source including (a) a pump        device having a pump operable to pressurize a working fluid        received from a low pressure source and deliver the pressurized        fluid, and an electric motor operable to drive the pump, and (b)        an accumulator for storing the pressurized fluid delivered from        the pump device;    -   a control valve device including a plurality of control valves        capable of controlling a pressure of the working fluid in a        brake cylinder, by utilizing the pressurized fluid delivered        from the power operated hydraulic pressure source, the plurality        of control valves including a pressure increasing control valve        disposed between the power operated hydraulic pressure source        and the brake cylinder, and a pressure reducing control valve        disposed between the brake cylinder and the low pressure source;        and    -   a holder structure which includes a first portion and a second        portion respectively having a first surface and a second surface        that are opposite to each other, the holder structure holding        the power operated hydraulic pressure source and the control        valve device such that a main body portion of each of the at        least two control valves is attached to the first portion, while        main body portions of the accumulator and the electric motor are        attached to the second portion, and such that a first row in        which the pressure increasing and pressure reducing control        valves are arranged and a second row in which the accumulator        and the electric motor are arranged are substantially parallel        to each other.

In the hydraulic braking pressure control unit according to the abovemode (27), the pressure increasing and pressure reducing control valves,electric motor and accumulator are arranged on the holder structure suchthat the first row consisting of the control valves and the second rowconsisting of the accumulator and the electric motor are substantiallyparallel to each other. This arrangement assures more effectiveutilization of the volume of the holder structure, than a randomarrangement of the control valves, accumulator and electric motor. Thus,the present arrangement permits a high degree of integration andsignificant reduction of size of the unit.

The direction of the first row is defined by a straight line connectingthe axes or centerlines of the pressure increasing and pressure reducingcontrol valves. Similar definition applies to the direction of thesecond row.

The hydraulic braking pressure control unit according to the above mode(27) may include the technical feature according to any one of the abovemodes (3), (4), (8)-(13), (15), (17) and (22).

(28) A hydraulic braking pressure control unit according to the abovemode (24), which includes a plurality of sets of control valves each setconsisting of the pressure increasing control valve and the pressurereducing control valve, and wherein the rows of the pressure increasingand pressure reducing control valves of the respective sets are parallelto each other.

In the unit according to the above mode (28) wherein the plurality ofsets of pressure increasing and pressure reducing valves are arranged inthe respective first rows parallel to each other, the volume of theholder structure is effectively utilized.

The pressure increasing and pressure reducing control valves may beeither arranged in a rectangular lattice pattern, or alternatively in azigzag pattern such that the adjacent three pressure increasing controlvalves are located at respective apexes of a first isosceles trianglewhile the adjacent three pressure reducing control valves are located atrespective apexes of a second isosceles triangle which is similar to thefirst isosceles triangle and spaced from the first isosceles triangle inthe direction of the first rows. Where the control valves are arrangedin the rectangular lattice pattern, a straight line along which theplurality of pressure increasing control valves are arranged and astraight line along which the plurality of pressure reducing controlvalves are arranged are parallel to each other, and these straight linesare perpendicular to the first rows.

(29) A hydraulic braking pressure control unit according to the abovemode (27) or (28), wherein the main body portions of the electric motorand the accumulator are located in an almost central part of the secondsurface, and the plurality of control valves attached to the firstportion are located on opposite sides of a plane which includes axes ofthe electric motor and the accumulator and which is perpendicular to thefirst and second surfaces.

Where the control valves are located on the opposite sides of anassembly of the accumulator and electric motor, a plurality of brakecylinder can be conveniently controlled by the control valves, byutilizing the pressurized fluid delivered from only one power operatedhydraulic pressure source.

The accuracy of control of the hydraulic braking pressure in the brakecylinders can be improved, particularly where the control valve deviceincludes a plurality of pressure increasing control valves which arearranged to control the pressure of the pressurized fluid received fromthe accumulator and apply the thus controlled fluid pressure to thebrake cylinders, and which control valves are located on the oppositesides of the accumulator located at the central portion of the secondsurface. This arrangement makes it possible to reduce a difference ofpressure losses between the accumulator and the individual pressureincreasing control valves. This, the arrangement according to the abovemode (29) permits the accumulator, electric motor and control valves tobe located at the optimum positions.

(30) A hydraulic braking pressure control unit according to any one ofthe above modes (27)-(29), further comprising at least one of (i) apressure relief valve disposed between high pressure and low pressuresides of the power operated hydraulic pressure source, (ii) an outputpressure detecting device operable to detect an output pressure of thepower operated hydraulic pressure source, and (iii) a brake cylinderpressure detecting device operable to detect the pressure in the brakecylinder, and wherein the above-indicated least one of the pressurerelief valve, the output pressure detecting device and the brakecylinder pressure detecting device is attached to the first portion ofthe holder structure.

The hydraulic braking pressure control unit according to the above mode(30) comprises at least one of the above-indicated pressure reliefvalve, output pressure detecting device and brake cylinder detectingdevice, in addition to the power operated hydraulic pressure source andthe control valve device. Accordingly, the function of the unit isimproved, so that a braking system including the unit can be simplifiedin construction.

The hydraulic braking pressure in the brake cylinder is controlled bythe control valves, by utilizing the pressurized fluid delivered fromthe power operated hydraulic pressure source. The control valves may becontrolled on the basis of the fluid pressure detected by the outputpressure detecting device and the hydraulic braking pressure detected bythe brake cylinder detecting device. Where electromagnetically operatedones of the control valves, the output pressure detecting device and thebrake cylinder detecting device are attached to the same portion of theholder structure, their lead wires can be comparatively easily bundledtogether.

While the pressure relief valve may be attached to the second portionrather than the first portion, it is usually more advantageous to attachthe pressure relief valve to the first portion.

(31) A hydraulic braking pressure control unit according to the abovemode (30), wherein the first surface and the second surface of theholder structure are parallel to each other, and the pressure reliefvalve and the output pressure detecting device attached to the firstplane are located near a plane which includes axes of the electric motorand the accumulator and which is perpendicular to the first and secondsurfaces.

The pressure relief valve is provided to prevent an excessive rise ofthe delivery pressure of the pump, while the output pressure detectingdevice is provided to detect the delivery pressure of the pump or thepressure of the pressurized fluid in the accumulator

In view of the functions of the pressure relief valve and the outputpressure detecting device, they are desirably disposed in a portion ofthe first surface which is near a portion of the second surface in whichthe electric motor and the accumulator are disposed. Where the electricmotor and the accumulator are disposed in an almost central part of thesecond surface, for instance, the output pressure detecting device andthe pressure relief valve are also located in an almost central part ofthe first surface, for example. This arrangement makes it possible toreduce the required lengths of the fluid passage connecting the pump andaccumulator to the pressure relief valve, and the fluid passageconnecting the pump and accumulator to the output pressure detectingdevice, so that these hydraulic components can be conveniently located.

(32) A hydraulic braking pressure control unit according to any one ofthe above modes (27)-(31), further comprising a master cylinder cut-offvalve operable between an open state for communication between the brakecylinder and a master cylinder operable to pressurize the working fluidto a pressure corresponding to a force of operation of a brake operatingmember by an operator, and a closed state for isolating the brakecylinder from the master cylinder, and wherein the master cylindercut-off valve is attached to the first portion of the holder structure.

Where the master cylinder cut-off valve is also attached to the holderstructure, the function of the unit can be further improved. A mastercylinder pressure detecting device operable to detect the pressure ofthe fluid in the master cylinder may also be attached to the firstportion of the holder structure.

(33) A hydraulic braking pressure control unit according to any one ofthe above modes (27)-(32), wherein the plurality of control valves areattached to the first portion such that axes of the control valve aresubstantially perpendicular to the first surface, while the electricmotor and the accumulator are attached to the second portion such thataxes of the electric motor and the accumulator are substantiallyperpendicular to the second surface.

Where the control valves include a master cylinder cut-off valve and apressure relief valve as described, these valves may also be attached tothe first portion such that their axes are substantially perpendicularto the first surface. Where the unit further includes an output pressuredetecting device, a brake cylinder pressure detecting device and amater-cylinder pressure detecting device, as described above, thesedetecting devices may also be attached to the first portion such thattheir axes are substantially perpendicular to the first surface. Sincethe first and second surfaces are parallel to each other, all of thehydraulic components held by the holder structure are attaché such thattheir axes are parallel to each other.

(34) A hydraulic braking pressure control unit according to any one ofthe above modes (27)-(33), wherein the holder structure has a lowpressure passage connected to the low pressure source, and a highpressure passage connected to the accumulator, the low pressure and highpressure passages being formed in an almost middle part of the holderstructure as seen in a plane of the second surface.

Where the accumulator and the electric motor are located in an almostmiddle part of the second surface, the high pressure passage connectedto the accumulator and the low pressure passage connected to the lowpressure source formed in the holder structure are located in the almostmiddle part of the second surface, as seen in the plane of the secondsurface.

The low pressure passage may be a passage formed in communication with asuction passage of the pump, or a passage formed in communicationthrough an exclusive port with a reservoir provided outside the presenthydraulic braking pressure control unit. Where the low pressure passageis held in communication with the suction passage of the pump, therequired number of the ports can be reduced, and the required size ofthe unit can be reduced.

(35) A hydraulic braking pressure control unit according to the abovemode (34), wherein the low pressure and high pressure passages areformed substantially parallel to each other.

The high pressure and low pressure passages may be parallel to eachother as seen in a direction perpendicular to the first and secondsurfaces, or as seen in a direction parallel to the first and secondsurfaces. In other words, the high pressure and low-low pressurepassages may be formed such that these passages are spaced from eachother as seen in the direction perpendicular to the first surface, orsuch that those passages overlap each other as seen in the directionperpendicular to the first surface, but are spaced apart from each otherin the direction perpendicular to the first surface.

(36) A hydraulic braking pressure control unit according to the abovemode (34) or (35), wherein the pressure reducing control valve is heldin communication with the low pressure passage, while the pressureincreasing valve is held in communication with the high pressurepassage.

(37) A hydraulic braking pressure control unit according to any one ofthe above modes (34)-(36), further comprising a pressure relief valvedisposed between high pressure and low pressure sides of the poweroperated hydraulic pressure source, and wherein the pressure reliefvalve is connected to both the low pressure and high pressure passages.

Where the pressure increasing control valve is held in communicationwith the high pressure passage while the pressure reducing control valveis held in communication with the low pressure passage, the pressurerelief valve is desirably disposed between the high pressure and lowpressure passages, for eliminating a need of providing an exclusivefluid passage for the pressure relief valve, so that the required numberof the fluid passages can be reduced, making it possible to reduce therequired size of the hydraulic braking pressure control unit.

The high pressure passage is usually provided with an output pressuredetecting device for detecting the output pressure of the power operatedhydraulic pressure source. In case, the pressure relief valve and theoutput pressure detecting device are disposed relatively close to eachother. The pressure relief valve is required to be held in communicationwith both of the high pressure and low pressure passages, while theoutput pressure detecting device is required to be disposed so as toprevent an interference with the low pressure passage. To this end, thehigh pressure and low pressure passages are connected to the respectivehigh pressure and low pressure ports of the pressure relief valve, forexample, so that the high pressure and low pressure passages areseparated from each other with the pressure relief valve interposedtherebetween. This arrangement permits the low pressure passage to beformed, so as to prevent an interference with the output pressuredetecting device. Thus, the pressure relief valve can be providedwithout forming an exclusive fluid passage, thereby making it possibleto reduce the required size of the unit.

(38) A hydraulic braking pressure control unit according to any one ofthe above modes (27)-(37), wherein the holder structure has a pluralityof brake cylinder passages which are held in communication with aplurality of brake cylinders, respectively and which are formed inparallel with each other.

The plurality of brake cylinder passages can be efficiently formed inthe holder structure, where the brake cylinder passages extend inparallel with each other. For instance, the high pressure and lowpressure passages are formed in an almost middle or central part of theholder structure, while the brake cylinder passages are formed onopposite sides of the high pressure and low pressure passages. Where abraking system including the present unit has two sub-systems, the brakecylinder passages may be formed such that the brake cylinder passageconnected to each brake cylinder of one of the sub-systems is/arelocated on one of the opposite sides of the passages, while the brakecylinder passage connected to each brake cylinder of the othersub-system is/are located on the other side. A similar arrangement isapplicable where a plurality of sets of pressure increasing and pressurereducing control valves are disposed along respective parallel firstrows corresponding to respective brake cylinders.

At least one master cylinder passage communicating with a mastercylinder may be formed in parallel with the brake cylinder passages.Each master cylinder passage may be spaced from the brake cylinderpassages as seen in a direction perpendicular to the first surface ofthe holder structure, or may overlap one of the brake cylinder passagesas seen in the direction perpendicular to the first surface, but arespaced from each other as seen in a direction parallel to the firstsurface.

(39) A hydraulic braking pressure control unit according to any one ofthe above modes (27)-(38), wherein the accumulator includes a housing, apartition member which fluid-tightly divides an interior of the housinginto two variable-volume chambers, and a connecting portion which isheld in communication with one of the two variable-volume chambers andwhich has two ports that are spaced from each other in an axialdirection of the housing, the two ports consisting of an inner portlocated at an end of the connecting portion, and an intermediate portlocated between the inner port and the one variable-volume chamber, andwhere the pressure increasing control valve is connected to the innerport while the pump device is connected to the intermediate port.

The pump and the pressure increasing control valve are connected to theaccumulator at different axial positions of the accumulator. In thisarrangement, a fluid passage connected to the pump and a fluid passageconnected to the pressure increasing control valve may be formed in theholder structure such that these two fluid passages overlap each otheras seen in the direction perpendicular to the second surface, but arespaced apart from each other as seen in the direction parallel to thesecond surface.

Each fluid passage is usually formed in the holder structure, so as toextend linearly in a direction parallel to the first or second surface.Accordingly, two hydraulic components connected to each other by thefluid passage are usually attached to the holder structure, withsuitable amounts of local embedment and projection of the components inand from the holder structure, such that two ports of the two componentsare located at the same position in the direction perpendicular to thesecond surface (in the direction of thickness of the holder memberbetween the first and second surfaces).

For instance, the amounts of local embedment and projection of theaccumulator and the pressure increasing control valve in and from theholder structure in the direction of thickness of the holder structure,and the positions in this direction of a delivery passage of the pumpand a supply passage connecting the accumulator and the pressureincreasing control valve are determined so that the discharge port ofthe pump and the pump-side port of the accumulator are located at thesame position in the direction of thickness of the holder structure (atthe same depth position from the first or second surface), while thecontrol-valve side port of the accumulator and the high pressure port ofthe pressure increasing control valve are located at the same positionin the direction of thickness.

(40) A hydraulic braking pressure control unit according to any one ofthe above modes (27)-(39), wherein each of the pressure increasingcontrol valve and the pressure reducing control valve has a highpressure port formed at one end thereof, and a low pressure port locatedbetween the above-indicated one end and other end as seen in an axialdirection of the control valve.

Each of the pressure increasing and pressure reducing control valvesincludes a connecting portion having the ports, and a solenoid. Theconnecting portion is a portion of a seating valve in which the portsare formed. The connecting portion and the solenoid are locatedrelatively near the inner and outer end portions of the control valve,respectively. Usually, the control valve is embedded at its inner endportion in the holder structure, while at least a portion of thesolenoid projects from the first surface of the holder structure. Thisarrangement is applicable to the master cylinder cut-off valve describedabove.

(41) A hydraulic braking pressure control unit according to any one ofthe above modes (27)-(40), wherein the holder structure further includesa third portion having a third surface which intersects said first andsecond surfaces, the holder structure having ports open in the thirdsurface, for connection to the low pressure source and the brakecylinder.

Where the plurality of ports for connection with the low pressure sourceand brake cylinder are open in one surface of the holder structure, thehydraulic braking pressure control unit can be easily installed on adesired member, such as a member of the body of an automotive vehiclefor which the unit is used.

In the unit according to the above mode (41), the electric motor and theaccumulator are desirably attached to the second portion of the holderstructure such that the electric motor is relatively near the thirdsurface while the accumulator is relatively distant from the thirdsurface. This arrangement is effective to reduce a resistance of flow ofthe working fluid from the low pressure source to the pump, and isaccordingly effective to reduce pressure pulsation of the pressurizedfluid delivered from the pump.

The pump driven by the electric motor may be a plunger pump or a gearpump. The port for connection with the master cylinder is desirablyformed to be open also in the third surface.

(42) A hydraulic braking pressure control unit according to any one ofthe above modes (27)-(41), further comprising at least one of (i) areservoir for storing the working fluid discharged from the brakecylinder, and (ii) a stroke simulator for connection to a mastercylinder, for flows of the working fluid between the stroke simulatorand the master cylinder as a pressurizing piston of the master cylinderis moved, and wherein the holder structure holds the above-indicated atleast one of the reservoir and the stroke simulator.

The reservoir and/or the stroke simulator may be attached to the holderstructure.

(43) A hydraulic braking pressure control unit comprising:

-   -   a power operated hydraulic pressure source including (a) a pump        device having a pump operable to pressurize a working fluid        received from a low pressure source and deliver the pressurized        fluid, and (b) an accumulator for storing the pressurized fluid        delivered from the pump device;    -   a control valve device including a plurality of control valves        capable of controlling a pressure of the working fluid in        respective brake cylinders, by utilizing the pressurized fluid        delivered from the power operated hydraulic pressure source, the        brake cylinders being operable to activate respective brakes for        braking respective wheels of a vehicle; and    -   a holder structure which holds the power operated hydraulic        pressure source and the control valve device and which includes        a first portion and a second portion respectively having a first        surface and a second surface which are opposed to each other,    -   and wherein the control valve device includes a plurality of        pressure increasing control valves disposed between the power        operated hydraulic pressure source and the brake cylinders,        respectively, and a plurality of pressure reducing control        valves disposed between the low pressure source and the brake        cylinders, respectively, and main bodies of the accumulator and        the electric motor are attached to an almost middle part of the        second surface of the holder structure, the plurality of        pressure increasing control valves and the plurality of pressure        reducing control valves consisting of two groups of control        valves which are attached to respective two areas of the first        surface which are located on opposite sides of a row in which        the accumulator and said electric motor are arranged on the        second surface.

The hydraulic braking pressure control unit according to the above mode(43) may include the technical feature according to any one of the abovemodes (3), (4), (8)-(3), (15), (17), (22), and (27)-(42).

(44) A holder structure of generally block shape for holding at leastone control valve, and a power operated hydraulic pressure sourceincluding (a) a pump device having a pump operable to pressurize aworking fluid received from a low pressure source and deliver thepressurized fluid, and (b) an accumulator for storing the pressurizedfluid delivered from the pump device, the holder structure having:

-   -   a first portion and a second portion respectively having a first        surface and a second surface which are opposed to each other;    -   at least one control-valve recess each of which is open in the        first surface, for receiving at least a portion of a        corresponding one of the at least one control valve;    -   an accumulator recess which is open in the second surface, for        receiving at least a portion of the accumulator;    -   a drive-force transmitting recess which is open in the second        surface, for receiving a drive-force transmitting portion of the        power operated hydraulic pressure source which is arranged to        transmit a rotary motion of the electric motor to the pump.

(45) A hydraulic braking pressure control unit comprising:

-   -   a power operated hydraulic pressure source including (a) a pump        device having a pump operable to pressurize a working fluid        received from a low pressure source and deliver the pressurized        fluid, and an electric motor operable to drive the pump, and (b)        an accumulator for storing the pressurized fluid delivered from        the pump device;    -   a control valve device including at least one control valve        capable of controlling a pressure of the working fluid in a        brake cylinder, by utilizing the pressurized fluid delivered        from the power operated hydraulic pressure source; and    -   a holder structure which holds the power operated hydraulic        pressure source and the control valve device.

In a braking system including the hydraulic braking pressure controlunit according to the above mode (45), the pressure of the fluid in thebrake cylinder is controlled by the control valve device, by utilizingthe pressurized fluid delivered from the power operated hydraulicpressure source. Where the control valve device controls a plurality ofbrake cylinders, at least one control valve may be provided for eachother the brake cylinders, or for two or more of the brake cylinders.

In the present hydraulic braking pressure control unit, the singleholder structure holds the power operated hydraulic pressure source andthe control valve device. The fluid pressure in each brake cylinder canbe controlled by controlling the power operated hydraulic pressuresource and the control valve device held by the single holder structure.

The holder structure preferably takes the form of a holder block,desirably, a generally hexahedron block. A hexahedron has three pairs ofopposite surfaces. However, the opposite surfaces of each pair may beeither parallel to each other or not parallel to each other. It ispossible that the opposite surfaces of one pair or each of two pairs areparallel to each other while the opposite surfaces of the other pair orpairs are not parallel to each other. Where the holder structure is arectangular parallelepiped, the opposite surfaces of each of the threepairs are parallel to each other. The volume of the holder structure canbe relatively efficiently utilized for forming fluid passages where theholder structure takes the form of a rectangular parallelepiped. Furtherthe fluid passages can be relatively easily formed in the rectangularparallelepiped. In addition, the control valve device and the poweroperated hydraulic pressure source can be easily attached to therectangular parallelepiped, and the hydraulic braking pressure controlunit can be easily attached to the body of a vehicle.

The hydraulic braking pressure control unit according to the above mode(45) may include the technical feature according to any one of the abovemodes (27-44).

(46) A hydraulic braking pressure control unit according to the abovemode (45), wherein the holder structure has a first portion and a secondportion respectively having a first surface and a second surface whichare opposed to each other, and holds the above-indicated at least onecontrol valve such that a main body portion of each control valve isfixed to the first portion of the holder structure, while main bodyportions of the accumulator and the electric motor are fixed to thesecond portion of the holder structure.

In the hydraulic braking pressure control unit according to the abovemode (46), the main body portion of each of the at least one controlvalve is attached to the first portion of the holder structure, whilethe main body portion of each of the electric motor and accumulator isattached to the second portion of the holder structure. Namely, theaccumulator is not disposed on a third portion having a third surfaceother than the first and second surfaces, the control valve device andthe power operated hydraulic pressure source can be efficiently disposedon the holder structure, so that the required size of the unit can bereduced.

Where the main body portion of the control valve is attached to thefirst portion of the holder structure, the control valve is usuallyattached to the holder structure such a portion of the main body portionis received in a recess open in the first surface while the remainingportion projects from the first surface. The portion received in therecess may be larger or smaller than the portion projecting from thefirst surface. In either case, the recess formed in the holder structuremay function as a part of the control valve. In this case, the recessand the main body portion constitute the control valve. Where the recessdoes not function as a part of the control valve, in other words, wherethe control valve is complete before attachment to the holder structure,the main body portion alone constitutes the control valve. The recessfunctioning as a part of the control valve may partially define a fluidchamber or a fluid passage. The above description is applicable to theaccumulator.

The electric motor may be attached to the holder structure such that adrive portion of the motor projects from the second surface while adrive-force transmitting portion of the motor is received in a hole openin the second surface. Where the pump is a plunger pump, for instance,an eccentric-cam portion serving as the drive-force transmitting portionof the electric motor is received in the hole, while the drive portionprojects from the second surface. The eccentric-cam portion may beconsidered to be an element of the pump. In this case, a rotationtransmitting portion which transmits a rotary motion of the driveportion to the eccentric-cam portion may be considered to be thedrive-force transmitting portion of the electric motor.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features, advantages and technical andindustrial significance of the present invention will be betterunderstood by reading the following detailed description of presentlypreferred embodiments of the invention, when considered in connectionwith the accompanying drawings, in which:

FIG. 1 is a circuit diagram of a braking system including a hydraulicbraking pressure control unit constructed according to one embodiment ofthis invention;

FIG. 2 is a schematic view of an accumulator provided in the hydraulicbraking pressure control unit of FIG. 1;

FIG. 3 is an elevational view in cross section schematically showing alinear control valve provided in the hydraulic braking pressure controlunit of FIG. 1;

FIG. 4 is a view schematically showing a general arrangement of thehydraulic braking pressure control unit;

FIG. 5 is a plane view of the hydraulic braking pressure control unit;

FIG. 6 is a cross sectional view of the pressure control unit takenalong line 6-6 of FIG. 5;

FIG. 7 is a cross sectional view of the pressure control unit takenalong line 7-7 of FIG. 5;

FIG. 8 is a cross sectional view of the pressure control unit takenalong line 8-8 of FIG. 5;

FIG. 9 is a cross sectional view of the pressure control unit takenalong line 9-9 of FIG. 5;

FIG. 10 is a cross sectional view of the pressure control unit takenalong line 10-10 of FIG. 5;

FIG. 11 is a cross sectional view of the pressure control unit takenalong line 11-11 of FIG. 5;

FIG. 12 is a cross sectional view of the pressure control unit takenalong line 12-12 of FIG. 5;

FIG. 13 is a cross sectional view of the pressure control unit takenalong line 13-13 of FIG. 5;

FIG. 14 is a cross sectional view of the pressure control unit takenalong line 14-14 of FIG. 5;

FIG. 15 is a circuit diagram of a braking system including a hydraulicbraking pressure control unit constructed according to anotherembodiment of this invention;

FIG. 16 is a plan view of the hydraulic braking pressure control unit ofFIG. 15;

FIG. 17 is a cross sectional view of the hydraulic braking pressurecontrol unit taken along line 17-17 of FIG. 16;

FIG. 18 is a cross sectional view of the pressure control unit takenalong line 18-18 of FIG. 16;

FIG. 19 is a cross sectional view of the pressure control unit takenalong line 19-19 of FIG. 16;

FIG. 20 is a perspective view of the pressure control unit of FIG. 16;and

FIG. 21 is a perspective view of the pressure control unit of FIG. 16.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring FIGS. 1-14, there will be described an automotive vehiclebraking system incorporating a hydraulic braking pressure control unitconstructed according to one embodiment of this invention. In FIG. 1,reference numeral 10 denotes a hydraulic braking pressure control unit.This hydraulic braking pressure control unit 10 (hereinafter referred tosimply as “unit 10”) includes a power operated hydraulic pressure source12, a hydraulic pressure control valve device 14 and a plurality ofhydraulic pressure sensors. The hydraulic pressure control valve device14 includes a plurality of hydraulic pressure control valves. The unit10 has a plurality of ports to which are connected a master cylinder 20,brake cylinders 22 for front wheels FL, FR, brake cylinders 24 for rearwheels RL, RR, and a master reservoir 26.

The master cylinder 20 is of a tandem type including two pressurizingpistons one of which is operatively connected to a brake operatingmember in the form of a brake pedal 30. The front surfaces of the twopressurizing pistons partially define respective pressurizing chambersto which are connected respective fluid passages 32, 34. The brakecylinder 22 for the front right wheel FR is connected through the unit10 to the fluid passage 32, while the brake cylinder 22 for the frontleft wheel FL is connected through the unit 10 to the other fluidpassage 34. In the present embodiment, the two pressurizing chambers areconnected to the two front wheel brake cylinders 22, respectively.

The power operated hydraulic pressure source 12 is connected to thebrake cylinders 22 for the front right and left wheels, and to the brakecylinders 24 for the rear right and left wheels. The front right andleft wheel brake cylinders 22 are connected to both of the mastercylinder 20 and the power operated hydraulic pressure source 12, whilethe rear right and left wheel brake cylinders 24 are not connected tothe master cylinder 20, but are connected to only the power operatedhydraulic pressure source 12. Hydraulic braking pressures in the wheelbrake cylinders 22, 24 are controlled by the plurality of pressurecontrol valves of the control valve device 14, by utilizing thepressurized fluid delivered from the power operated hydraulic pressuresource 12.

The fluid passage 32 consists of a first portion between the mastercylinder 20 and the unit 10, a second portion formed within the unit 10,and a third portion between the unit 10 and the front right wheel brakecylinder 22. The first portion is connected to a port 40 of the unit 10,while the third portion is connected to a port 41 of the unit 10.Similarly, the fluid passage 34 consists of a first portion connectingthe master cylinder 20 and a port 42 of the unit 10, a second portionformed through the unit 10, and a third portion connecting a port 43 ofthe unit and the front left wheel brake cylinder 22.

The rear right wheel brake cylinder 24 is connected through a fluidpassage to a port 44 of the unit 10, while the rear left wheel brakecylinder 24 is connected through a fluid passage to a port 45 of theunit 10.

The power operated hydraulic pressure source 12 includes a pump device50, and an accumulator 52. The pump device 50 includes a plunger pump 54of two cylinder type (hereinafter referred to simply as “pump 54”), anelectric motor 56 serving as a pump motor to drive the pump 54, and aneccentric cam portion (not shown) serving as a drive-force transmittingportion. The pump 54 has two cylinders. The eccentric cam portion has aneccentric cam which is rotated by a drive force produced by the motor56, to reciprocate pistons within the respective two cylinders. The pump54 is connected to the master reservoir 26 through a reservoir passage60, so that the pump 54 is operated to pressurize a working fluidreceived from the master reservoir 26.

To the discharge side of the pump 54, there is connected the accumulator52, which stores or accommodates the pressurized fluid delivered fromthe pump 54. The pressure of the pressurized fluid stored in theaccumulator 52 is detected by an accumulator pressure sensor 62. Themotor 56 is controlled such that the pressure detected by theaccumulator pressure sensor 62 is held within a predetermined range.

A fluid passage connecting the discharge side of the pump 54 and thereservoir passage 60 is provided with a pressure relief valve 64, whichis provided to prevent an excessive rise of the delivery pressure of thepump 54. The reservoir passage 60 has a portion connecting the masterreservoir 26 and a port 66 of the unit 10.

As shown in FIG. 2, the accumulator 52 includes an accumulator portion70 and a connecting portion 72. The accumulator portion 70 is of bellowstype, including a housing 73 and a partition member 76 which divides theinterior space of the housing 73 into two variable-volume chambers 74,75. The partition member 76 consists of a metallic bellows 76 a, abottom plate 76 b and a sealing member 76 c. The variable-volume chamber74 (gas chamber) is charged with a high pressure gas, while the othervariable-volume chamber 75 is used to store the pressurized fluiddelivered from the pump 54.

The connecting portion 72 has two ports 77, 78 which are spaced fromeach other in the axial direction of the accumulator 52. The port 77 atthe end of the connecting portion 72 is connected to pressure increasinglinear control valves 84 (which will be described), while the port 78 atan intermediate part of the connecting portion 72 is connected to thepump 54.

The hydraulic pressure control valve device 14 includes twosolenoid-operated shut-off valves 80, 82 and four sets of linear controlvalves 84, 86. Each of the shut-off valves 80, 82 is selectively openedand closed to selectively permit and inhibit a flow of the fluidtherethrough, upon application and removal of an electric current to andfrom its coil. Each of the linear control valves 84, 86 is capable ofcontinuously controlling a pressure difference on its opposite sides.

Each of the shut-off valves 80, 82 and linear control valves 84, 86 hastwo ports communicating with the appropriate fluid passages. The twoports are spaced from each other in the axial direction of the valve.

The solenoid-operated two shut-off valves 80, 82 are provided betweenthe master cylinder 20 and the respective brake cylinders 22 for thefront right and left wheels, to selectively permit and inhibitcommunication of the wheel brake cylinders 22 with the master cylinder20. In this sense, the solenoid-operated shut-off valves 80, 82 may becalled master cylinder cut-off valves.

The four sets of linear control valves 84, 86 are provided for therespective four wheel brake cylinders 22, 24. The linear control valve84 of each set, which serves as pressure increasing linear controlvalve, is provided in a fluid passage 88 connecting the correspondingwheel brake cylinder 22, 24 and the accumulator 52. The other linearcontrol valves 86 of the set, which serves as a pressure reducing linearcontrol valve, is provided in a fluid passage 89 connecting thecorresponding wheel brake cylinder 22, 24 and the reservoir 26. In thepresent embodiment, the hydraulic braking pressure in each wheel brakecylinder 22, 24 is controlled by the pressure increasing and pressurereducing linear control valves 84, 86, by utilizing the pressurizedfluid delivered from the power operated hydraulic pressure source 12,while the solenoid-operated shut-off valves 80, 82 are held in theclosed state (that is, while the wheel brake cylinder 22, 24 is isolatedfrom the master cylinder 20).

As shown in FIG. 3, each of the pressure increasing and pressurereducing linear control valves 84, 86 includes a seating valve 90, and asolenoid 93 provided with a coil 92. The seating valve 90 has a highpressure port 94 at its end, and a low pressure port 96 at an axiallyintermediate portion thereof.

The seating valve 90 has a valve seat 100, a valve member 102 movabletoward and away from the valve seat 100, and a spring 104 biasing thevalve member 102 in a direction that causes the valve member 102 to beseated on the valve seat 100. The high pressure port 94 is open in thevalve seat 100. While no electric current is applied to the coil 92, thevalve member 102 is held seated on the valve seat 100, under a biasingaction of the spring 104, so that the seating valve 90 is held in theclosed state. While an electric current is applied to the coil 92, thesolenoid 93 produces an electromagnetic force acting on the valve member102 in a direction that cause the valve member 102 to be moved away fromthe valve seat 100. At the same time, a force based on a differencebetween the fluid pressures at the high pressure and low pressure ports94, 97 acts on the valve member 102 in the direction to cause themovable member 102 to be moved away from the valve seat 100. A positionof the valve member 102 relative to the valve seat 100 is determined bythe electromagnetic force, the biasing force of the spring 104 and theforce based on the pressure difference, so that the pressure differenceacross the seating valve 90 can be controlled by controlling the amountof electric current to be applied to the coil 90.

A portion of the seating valve 90 having the high pressure port 94 andthe low pressure port 96 constitutes a connecting portion 106. In thepresent embodiment, the entirety of each of the pressure increasinglinear control valves 84 and the pressure reducing linear control valves86 is considered to be a main body portion of a control valve which iscapable of functioning to control the hydraulic braking pressure in thecorresponding wheel brake cylinder 22, 24.

Each pressure increasing linear control valve 84 is connected at itshigh pressure port 94 to the power operated hydraulic pressure source12, and at its low pressure port 96 to the corresponding wheel brakecylinder 22, 24. On the other hand, each pressure reducing linearcontrol valve 96 is connected at its high pressure port 94 to thecorresponding wheel brake cylinder 22, 24, and at its low pressure port96 to the reservoir 26.

Each of the master cylinder cut-off valves 80, 82 described aboveincludes a seating valve and a solenoid, and is similar in arrangementwith the linear control valves 84, 86. However, the master cylindercut-off valves 80, 82 are different from the linear control valves 84,86 in that the cut-off valves 80, 82 are merely opened and closed uponenergization and deenergization of a solenoid coil, without a control ofthe amount of electric current applied to the coil, and in that thevalve member is biased by a spring, in a direction that causes the valvemember to be moved away from the valve seat. Each master cylindercut-off valve 80, 82 is a normally open valve which is held in the openstate while the coil is in the deenergization state.

The pressure of the pressurized fluid delivered from the master cylinder20 is detected by two master cylinder pressure sensors 120, while thepressures of the fluid in the wheel brake cylinders 22, 24 are detectedby respective four brake cylinder pressure sensors 122. The two mastercylinder pressure sensors 120 are connected to the respective twopressurizing chambers of the master cylinder 20, while the four brakecylinder pressure sensors 122 are connected to the respective fluidpassages connected to the respective four wheel brake cylinders 22, 24.

The fluid passage 32 is provided with a stroke simulator device 140,which includes a stroke simulator 142 and a simulator control valve 144.While the master cylinder cut-off valves 80, 82 are held in the closedstate, the fluid delivered from the master cylinder 20 is absorbed inthe stroke simulator 142, so that the brake pedal 30 can be operatedsuch that its operating stroke is increased with the operating force,even in the closed state of the cut-off valves 80, 82.

As shown in FIG. 4, the unit 10 uses a holder block 150 as a holderstructure, which takes the form of a generally hexahedron block, moreprecisely a generally rectangular parallelepiped. The unit 10 consistsof this holder block 150, and the control valves 64, 80, 82, 84, 86,pressure sensors 62, 120, 122, power operated hydraulic pressure source12, etc. which are attached to the holder block 150 as described belowin detail. The unit 10 which is thus obtained as a single structure andwhich includes the power operated hydraulic pressure source 12 as wellas the control valves and pressure sensors is capable of functioning asa high-performance hydraulic braking pressure control unit operable tocontrol the hydraulic braking pressures in the wheel brake cylinders 22,24.

The holder block 150 has three pairs of parallel opposed surfaces.Namely, the holder block 150 has a first surface 152 (parallel to an XYplane), a second surface 154 parallel to the first surface 152, a thirdsurface 155 (parallel to an XZ plane) perpendicular to the first andsecond surfaces 152, 154, a fourth surface 156 parallel to the thirdsurface 155, as shown in FIG. 4, and a fifth and a sixth surface 170,171 as shown in FIG. 8, for example. The fifth surface 170 (parallel toa YZ plane) is perpendicular to the first through fourth surfaces 152,154, 155, 156, and the sixth surface 171 is parallel to the fifthsurface 170. The holder block 150 includes six side portionsrespectively having the first through sixth surfaces 152, 154,155,156,170, 171.

To the first surface 152 of the holder block 150, there are attached theelectromagnetically operated control valves such as the pressureincreasing linear control valves 84 and pressure reducing linear controlvalves 86, and the pressure sensors such as the brake cylinder pressuresensors 122. To the second surface 154, there are attached the motor 56and the accumulator 52. For example, each electromagnetically operatedcontrol valve is mounted on the first surface 152 such that at least theconnecting portion (106) of the control valve is received in a mountingrecess formed in the first surface 152, while at least a portion of thesolenoid portion of the control valve projects from the first surface152. Similarly, the accumulator 52 is mounted on the second surface 154such that at least the connecting portion 72 of the accumulator 52 isreceived in a mounting recess formed in the second surface 154 while atleast a portion of the accumulator portion 70 projects from the secondsurface 154.

The third surface 155 has the ports 40-45 and 66 described above. Theholder block 150 is attached at its fourth surface 156 to the body ofthe automotive vehicle. Since all of the ports are open in the thirdsurface 155, the holder block 150 can be easily attached to the vehiclebody.

As shown in FIGS. 5-8, the holder block 150 has a master cylinderpassage 158 communicating with the port 40, and a brake cylinder passage160 communicating with the port 41. The master cylinder passage 158 andthe brake cylinder passage 160 are connected to each other through themaster cylinder cut-off valve 80. The master cylinder passage 158 andthe brake cylinder passage 160 constitute the above-indicted secondportion of the fluid passage 32, which is formed through the unit 10 orholder block 150. Reference numeral 162 denotes master cylinder cut-offvalve recesses which are formed in the first surface 152, for attachingthe master cylinder cut-off valves 80, 82.

The master cylinder cut-off valve recess 162, master cylinder passage158 and brake cylinder passage 160 are formed such that the mastercylinder cut-off valve 80 attached at the master cylinder cut-off valverecess 162 is held at one of its ports with the master cylinder passage158, and at the other port with the brake cylinder passage 160 through acommunication passage 163.

The first surface 152 also has a master cylinder pressure sensor recess164 and a brake cylinder pressure sensor recess 165, which are providedfor the fluid passage 32. The master cylinder pressure sensor recess 164is formed such that a detecting portion of the master cylinder pressuresensor 120 attached at the recess 164 is held in communication with themaster cylinder passage 158. The brake cylinder pressure sensor recess165 is formed such that a detecting portion of the brake cylinderpressure sensor 122 attached to the recess 165 is held in communicationwith the brake cylinder passage 160. The master cylinder passage 158 andthe brake cylinder passage 160 are formed so as to extend in the Y-axisdirection.

The master cylinder cut-off valve recess 162, master cylinder pressuresensor recess 164 and brake cylinder recess 165 are also provided forthe master cylinder passage 158 communicating with the port 42 of theunit 10 and the brake cylinder passage 160 communicating with the port43. These passages 158, 160 constitute the above-indicated secondportion of the fluid passage 34 formed through the unit 10 (holder block150). The master cylinder cut-off valve 82 is disposed between thesepassages 158, 160.

The ports 44 and 45 are held in communication with respective brakecylinder passages 166 connected to the rear left and right wheel brakecylinders 24. The brake cylinder passages 166 are not in communicationwith the master cylinder passage 158. The brake cylinder passages 160,166 are provided with the pressurized working fluid which is deliveredfrom the power operated hydraulic pressure source 12 and the pressure ofwhich is controlled by the pressure increasing and pressure reducinglinear control valves 84, 86. In this sense, the brake cylinder passages160, 166 may be called controlled-pressure passages.

The brake cylinder passages 166 are formed so as to extend in the Y-axisdirection, in parallel with the brake cylinder passages 160, such thatthe passages 166 are spaced from the passages 160 in the X-axisdirection, and are located at the same Z-axis position as the passages160. Each of the two master cylinder passages 158 is formed between thecorresponding two brake cylinder passages 160, 166 such that the mastercylinder passage 158 is spaced from the brake cylinder passages 160, 166in the Z-axis direction.

The holder block 150 further has a pump recess 167 formed therein, asshown in FIGS. 5 and 9. This pump recess 167 includes an eccentric-camrecess 168 and two cylinder recesses 169. The eccentric-cam recess 168is provided for receiving the eccentric cam portion of the pump device50, which serves as the drive-force transmitting portion. The twocylinder recesses 169 are provided for receiving the respective twopistons of the pump 54.

As shown in FIG. 9, the eccentric-cam recess 168 is open in the secondsurface 154, while the two cylinder recesses 160 are open in therespective fifth and sixth surfaces 170, 171 (parallel to the YZ plane)which are parallel to each other.

The pump 54 is mounted on the fifth and sixth surfaces 170, 171 suchthat the two pistons are received in the respective cylinder recesses169, while the motor 56 is mounted on the second surface 154 such thatthe eccentric cam portion connected to the motor 56 is received in theeccentric-cam recess 168.

The holder block 150 further has two discharge passages 172 incommunication with respective two discharge portions communicating withthe two cylinders of the pump 54. The two discharge passages 172 areconnected to a delivery passage 174 through respective connectingpassages 173, so that the fluid masses pressurized in the two cylindersmerge with each other into a single mass of the pressurized fluid, whichis fed into the accumulator 52. This arrangement is effective tominimize pressure pulsation of the pressurized fluid delivered from thepump 54.

The holder block 150 further has a suction passage 176 in communicationwith the suction side of the pump 54, that is, with the eccentric-camrecess 168, as shown in FIGS. 5 and 8. The suction passage 176 is heldin communication with the master reservoir 26 through the port 66.

The suction passage 176 and delivery passage 174 are formed so as toextend in the Y-axis direction, in parallel with each other, in analmost central part of the holder block 150 as seen in the X-axisdirection. The discharge passages 172 are also formed so as to extend inthe Y-axis direction.

Reference numeral 180 denotes an accumulator recess 180 formed to beopen in the second surface 154. As shown in FIG. 10, the intermediateport 78 of the accumulator 52 attached at the accumulator recess 180 isheld in communication with the delivery passage 174, and while the innerport 77 of the accumulator 52 is held in communication with a supplypassage 182, as shown in FIG. 11. The holder block 150 further has apressure increasing passage 184 formed so as to intersect the supplypassage 182 substantially at right angles. The pressure increasinglinear control valves 84 are connected to the pressure increasingpassage 184. The supply passage 182 is formed in parallel with thedelivery passage 174 and in alignment with the delivery passage 174 inthe X-axis direction, such that these passages 182, 174 are spaced fromeach other in the Z-axis direction. Thus, the supply passage 182 is alsolocated at the almost central part of the holder block 150 as seen inthe X-axis direction. The pressure increasing passage 184 is formed soas to extend in the X-axis direction.

The holder block 150 further has a relief-valve recess 186 and anaccumulator-pressure sensor recess 187, which are open in the firstsurface 152. The pressure relief valve 64 and the accumulator pressuresensor 62 are attached at the respective recesses 186, 187 open in thefirst surface 152.

The holder block 150 also have four pressure increasing valve recesses188 formed in communication with the pressure increasing passage 184.These recesses 188 are spaced apart from each other by suitabledistances along the pressure increasing passage 184, as shown in FIG. 5.

As shown in FIGS. 6 and 12, the high pressure port 94 of each pressureincreasing linear control valve 84 attached at the correspondingpressure increasing valve recess 188 is held in communication with thepressure increasing passage 184, while the low pressure port 96 of thevalve 84 is held in communication with the corresponding brake cylinderpassage 160, 166. In the present embodiment, each pressure increasinglinear control valve 84 is attached at the corresponding recess 188 suchthat the linear control valve 84 is held in communication with thesupply passage 182 through the pressure increasing passage 184, so thatthe pressurized fluid in the supply passage 182 is supplied to the highpressure port 94 of the valve 84 through the pressure increasing passage184.

In the present embodiment, the supply passage 182, pressure increasingpassage 184 and brake cylinder passage 166 (160) constitute the fluidpassage 88. The supply passage 182 and the pressure increasing passage184 are provided commonly for the four wheel brake cylinders 22, 24,while the four brake cylinder passages 160, 166 are provided for therespective four wheel brake cylinders 22, 24. The brake cylinderpassages 160 constitute the above-indicated third portion of the fluidpassages 32, 34, as well as the fluid passage 88.

The holder block 150 further has a low pressure passage 200 formed incommunication with the suction passage 176 through the eccentric-camrecess 168, as shown in FIG. 14. The low pressure passage 200 is formedin parallel with the delivery passage 174 and the supply passage 182, inthe almost central part of the holder block 150 as seen in the X-axisdirection, such that the low pressure passage 200 is spaced from thepassages 174, 182 in the Z-axis direction.

The holder block 150 also has a pressure reducing passage 202 formed soas to intersect the low pressure passage 200 substantially at rightangles. The holder block 150 also has four pressure reducing valverecesses 204 open in the first surface 152, such that the recesses 204are spaced apart from each other by suitable distances along thepressure reducing passage 202. The high pressure port 94 of eachpressure reducing linear control valve 86 attached at the correspondingpressure reducing valve recess 204 is held in communication with acommunication passage 206 (a part of the brake cylinder passage 160 or166), while the low pressure port 96 of each valve 86 is held incommunication with the pressure reducing passage 202. In thisembodiment, the pressure reducing linear control valves 86 are attachedat the respective recesses 204 such that each valve 86 is held incommunication with the low pressure passage 200 through the pressurereducing passage 202, so that the fluid is discharged from the lowpressure port 96 to the reservoir 26 through the pressure reducingpassage 202, the low pressure passage 200 and the suction passage 176.

The brake cylinder passages 166 (160), pressure reducing passage 202,low pressure passage 200 and suction passage 176 constitute the fluidpassage 89. Like the supply passage 182 and pressure increasing passage184 described above, the suction passage 176, low pressure passage 200and pressure reducing passage 202 are provided commonly for the fourwheel brake cylinders 22, 24, while the four brake cylinder passages160, 166 are Z provided for the respective wheel brake cylinders 22, 24.

As described above, the holder block 150 has the plurality of fluidpassages and the plurality of mounting recesses. Most of the fluidpassages are formed so as to extend in the XY plane, at the same Z-axisposition. The fluid passages and the mounting recesses are formed suchthat the fluid passages are held in communication with the respectiveports of the connecting portions of the control valves and accumulatorattached at the respective mounting recesses. Accordingly, the requiredZ-axis positions of the fluid passages are determined by the Z-axispositions of the connecting portions and the depths (Z-axis positions)of the mounting recesses. In other words, the mounting recesses andfluid passages are formed for communication of the fluid passages withthe ports of the control valves and accumulator as attached to therecessed portions of the holder block 150.

The above-indicated relief-valve recess 186 is formed between the supplypassage 182 and the low pressure passage 200. As described above, thepressure-relief valve 64 is provided to prevent an excessive rise of thedelivery pressure of the pump 54, and is therefore required to belocated close to the accumulator 52 and pump 54. The low pressurepassage 200 is utilized for the pressure-relief valve 64, without theprovision of an exclusive low pressure passage 200 for thepressure-relief valve 64. Further, since the accumulator pressure sensor62 is provided to detect the fluid pressure in the supply passage 182,the accumulator-pressure sensor recess 187 is required to be formed soas to avoid an interference with the low pressure passage 200.

In the holder block 150, the low pressure passage 200, supply passage182, relief-valve recess 186 and accumulator pressure sensor 187 areformed, so as to meet the requirements described above, namely, suchthat the supply passage 182 is held in communication with the inner highpressure port of the pressure-relief valve 64 attached at therelief-valve recess 186, and is located as close as possible to theaccumulator-pressure sensor recess 187, while the low pressure passage200 is held in communication with the intermediate low pressure port ofthe pressure-relief valve 64, and is located as far as possible from theaccumulator-pressure sensor recess 187. Therefore, the low pressurepassage 200 is spaced apart from the supply passage 182 in the X-axisdirection, such that the passage 200 is located as far as possible fromthe accumulator-pressure sensor recess 187. In this arrangement, thepressure-relief valve 64 can be located between the supply passage 182and the low pressure passage 200, without having to provide an extrafluid passage, and so as to avoid a problem that the accumulatorpressure sensor 62 attached in communication with the supply passage 182interferes with the low pressure passage 200 and the pressure-reliefvalve 64. Accordingly, the number of the required fluid passages can bereduced, leading to a reduced size of the unit 10.

In the present embodiment, the brake cylinder passages 160, 166 areformed so as to extend in parallel with each other, and these brakecylinder passages 160, 166, delivery passage 174, low pressure passage200, supply passage 182 and suction passage 176 are formed in parallelwith each other, as shown in FIG. 5. Further, the pressure increasingpassage 184 and the pressure reducing passage 202 are formed so as toextend in the direction perpendicular to the supply passage 182 and thelow pressure passage 200, and the pressure increasing linear controlvalves 84 are arranged along the pressure increasing passage 184 whilethe pressure reducing linear control valves 86 are arranged along thepressure reducing passage 202. Thus, the four pressure increasing linearcontrol valves 84 and the four pressure reducing linear control valves86, which are provided for the respective four wheel brake cylinders 22,24, are arranged in a rectangular lattice pattern, such that fourstraight lines passing the axes of the respective sets of control valves84, 86 are parallel to each other. In addition, since the brake cylinderpassages 160, 166 are parallel to each other, four lines passing theaxes of the respective sets of control valves 84, 86 and brake cylinderpressure sensors 122 are almost parallel to each other.

The row of four pressure increasing linear control valves 84 and the rowof four pressure reducing linear control valves 86 are parallel to eachother.

Thus, the various electromagnetically operated control valves and thevarious pressure sensors are arranged in a considerably integratedfashion, so as to effectively reduce the required size of the unit 10 orholder block 150.

Further, the delivery passage 174, low pressure passage 200 and supplypassage 182 are located at an almost central part of the holder block150 as seen in the X-axis direction, so that the two sets of pressureincreasing and pressure reducing linear control valves 84, 86 can bedisposed on either each of the opposite sides of the delivery, lowpressure and supply passages 174, 200, 182. Accordingly, the requiredlength of the fluid passages 88, 89 connected to the wheel brakecylinders 22, 24 can be reduced.

In the present embodiment, at least one of the delivery passage 174 andthe supply passage 182 constitutes a high pressure passage.

Further, the ports 77 and 78 of the connecting portion 72 of theaccumulator 52 are spaced apart from each other in the axial directionof the accumulator 52. The accumulator recess 180, pressure increasingvalve recesses 188, delivery passage 174, supply passage 182 andpressure increasing passage 184 are required to be formed such that thedelivery passage is communicated with the port 78, and the supplypassage 182 is communicated with the port 77, while the pressureincreasing passage 184 perpendicular to the supply passage 182 iscommunicated with the high pressure port 94 of each pressure increasinglinear control valve 84. With the recesses 188, 188 and passages 174,182, 184 being thus formed to meet the above-indicated requirement, theamount of projection of the accumulator 52 from the second surface 154(which amount corresponds to the amount of projection of the eccentriccam portion of the motor 56 from the second surface 154), and the amountof projection of each pressure increasing linear control valve 84 fromthe first surface 152 are determined. In other words, the amounts ofprojection of the pressure increasing linear control valves 84 and theaccumulator 52 change depending upon whether the two ports 77, 78 of theconnecting portion 72 of the accumulator 52 are axially spaced apartfrom each other as in the present embodiment, or not. The axiallyspaced-apart relationship of the two ports 77, 78 can reduce adifference between the amounts of projection of the control valves 84and the accumulator 52.

Reference numeral 250 in FIG. 5 denotes openings which are provided todefine fluid passages and which are closed by plugs.

The unit 10 is controlled by a hydraulic pressure control device 300,which is principally constituted by a computer. The hydraulic pressurecontrol device 300 includes a CPU 302, a ROM 304, a RAM 306 and ininput-output portion 308. To the input-output portion 308, there areconnected the pressure sensors 62, 120, 122, the coils of theelectromagnetically operated control valves 80, 82, 84, 86 and the motor56.

Since the unit 10 incorporates the power operated hydraulic pressuresource 12, the hydraulic pressure control device 300 controls only theunit 10. Further, the control valves 80, 82, 84, 86 and the pressuresensors 62, 120, 122 are mounted on the same surface of the holder block150, the lead wires of these control valves and pressure sensors can becomparatively easily bundled together.

The unit 10 according to the present first embodiment includes thepressure increasing linear control valves 84 and the pressure reducinglinear control valves 86. These linear control valves may be replaced byshut-off valves that are simply opened and closed to control thehydraulic braking pressures in the wheel brake cylinders. While theplunger pump 54 is used in the first embodiment, a gear pump may be usedin the pump device. Further, the principle of the invention isapplicable to any braking system other than the braking system describedabove, for example, to a braking system wherein each of two pressurizingchambers of the master cylinder 20 is connected to two brake cylinders.While the accumulator 52 of bellows type is used in the firstembodiment, the unit 10 may include an accumulator of bladder type inwhich the partition member is formed of a flexible material such as arubber material, or an accumulator of piston type in which the partitionmember is a piston.

In the embodiment described above, the holder block 150 of the unit 10is attached at its fourth surface 156 to the vehicle body. However, theholder block 150 may be attached to the vehicle body, at its fifthsurface 170 or sixth surface 171, or at two or three surfaces selectedfrom the fourth, fifth and sixth surfaces 156, 170, 171. The shape ofthe holder block 150 is not limited to that in the illustratedembodiment. Further, the stroke simulator device 140 and other hydrauliccomponents may be attached to the holder block 150, as well as thevalves 64, 80, 82, 84, 86, pressure sensors 62, 120, 122 and poweroperated hydraulic pressure source 12.

Referring next to FIGS. 15-21, there will be described a secondembodiment of this invention. In FIG. 15, reference numeral 310 denotesa brake pedal serving as a brake operating member, and reference numeral312 denotes a master cylinder equipped with a hydraulic booster, whichis arranged to deliver a pressurized working fluid, upon operation ofthe brake pedal 310 by the operator of an automotive vehicle. Further,reference numeral 314 denotes a power operated hydraulic pressure sourcearranged to deliver a pressurized fluid, when the hydraulic pressuresource is supplied with an electric energy. Reference numeral 316denotes a hydraulic braking pressure control unit constructed accordingto the second embodiment of the invention and capable of controllinghydraulic braking pressures in brake cylinders 320, 321 for front leftand right wheels FL, FR and brake cylinders 322, 323 for rear left andright wheels RL, RR, by utilizing the pressurized fluid delivered fromthe power operated hydraulic pressure source 314.

The master cylinder 312 with the hydraulic booster (hereinafter referredto as “master cylinder 312”) includes a hydraulic booster portion 330and a master cylinder portion 332. The hydraulic booster portion 330 isarranged to receive the pressurized fluid received from the poweroperated hydraulic pressure source 314, for generating a fluid pressurecorresponding to a boosted operating force of the brake pedal 310. Themaster cylinder portion 332 has pressurizing pistons and is arranged todeliver a pressurized fluid the pressure of which corresponds to abraking force applied to the pressurizing pistons, as boosted by thefluid pressure generated by the hydraulic booster portion 330.

To the hydraulic booster 330, there is connected through a fluid passage334 the rear right wheel brake cylinder 323. To the master cylinderportion 332, there is connected through a fluid passage 336 the frontright wheel brake cylinder 321. The master cylinder portion 332 iscapable of generating a fluid pressure corresponding to the operatingforce of the brake pedal 310, even in the event of occurrence of anyabnormality or defect of the power operated hydraulic pressure source314.

The power operated hydraulic pressure source 314 includes a pump device344, an accumulator 346 and an accumulator pressure sensor 348. The pumpdevice 344 includes a pump 340, and a pump motor 342 to drive the pump340. The pump 40 is arranged to pressurize the working fluid receivedfrom a reservoir 350, and the pressurized fluid delivered from the pump340 is stored or accommodated in the accumulator 346. The accumulator346 is constructed as shown in FIG. 2. The pump motor 342 is controlledsuch that the pressure of the fluid stored in the accumulator 348, thatis, the fluid pressure as detected by the accumulator pressure sensor348 is held within a predetermined range. Between the reservoir 350 andthe delivery port of the pump 340, there is provided a pressure reliefvalve 352, for preventing an excessive rise of the pressure of thepressurized fluid delivered from the pump 340.

To the power operated hydraulic pressure source 314, there are connectedthrough a high pressure passage 356 the brake cylinders 320-323 for thefront left and right wheels FL, FR and rear left and right wheels RL,RR. In the present second embodiment, all of the four wheel brakecylinders 320-323 are connected to the power operated hydraulic pressuresource 314, while the front and rear right wheel cylinders 321, 323 areconnected to the master cylinder 312. Further, the front left and rightwheel brake cylinders 320, 321 are connected to each other by aconnecting passage 358, while the rear left and right wheel brakecylinders 322, 323 are connected to each other by a connecting passage360. The connecting passages 358, 360 are provided with respectivecommunication control valves 362, 364, which are normally open valves tobe held open when no electric currents are applied thereto. The frontleft and right wheel brake cylinders 320, 321 are held in communicationwith each other while the communication control valve 362 is in the openstate, and are isolated from each other while the valve 362 is in theclosed state. Similarly, the rear left and right wheel brake cylinders322, 323 are held in communication with each other while thecommunication control valve 364 is in the open state, and are isolatedfrom each other while the valve 364 is in the closed state. Thus, thepresent braking system has two mutually independent sub-systems one ofwhich includes the front wheel brake cylinders 320, 321 and the other ofwhich includes the rear wheel brake cylinders 322, 323 k.

Between the power operated hydraulic pressure source 314 and the frontleft and right wheel brake cylinders 320, 210 and the rear left andright wheel brake cylinders 322, 323, there are disposed respectivebraking pressure control valve devices 370, 371, 372 and 373. Each ofthese pressure control valve devices 370-373 includes a pressureincreasing control valve 378 and a pressure reducing control valve 380.The pressure increasing control valves 378 are disposed in a highpressure passage 356 between the wheel brake cylinders 320-323 and thepower operated hydraulic pressure source 314, while the pressurereducing control valves 380 are disposed in a low pressure passage 384between the wheel brake cylinders 320-323 and the reservoir 350. Fourbrake cylinder pressure sensors 386, 388 are provided for the four wheelbrake cylinders 320-323, respectively, so that the fluid pressures inthe wheel brake cylinders 320, 321 are detected by the respectivepressure sensors 386, while the fluid pressures in the wheel brakecylinders 322, 323 are detected by the respective pressure sensors 388.

The pressure increasing control valves 378 and the pressure reducingcontrol valves 380 are linear control valves identical with the linearcontrol valves 84, 86 which have been described above by reference toFIG. 3. Each pressure increasing control valve 378 is connected at itshigh pressure port 94 (FIG. 3) to the high pressure passage 356 (poweroperated hydraulic pressure source 314), and at its low pressure port 96(FIG. 3) to the corresponding wheel brake cylinder 320, 321, 322, 323. Afluid pressure difference across the pressure increasing control valve378 is obtained as a difference between a fluid pressure detected by apressure sensor 406 connected to a portion of the high pressure passage356 between the control valve 378 and the accumulator 346, and a fluidpressure detected by the brake cylinder pressure sensor 386, 688.Although the pressure sensor 406 is provided to detect the outputpressure of the power operated hydraulic pressure source 314, thispressure sensor 406 is located nearer to the control valve 378 than theaccumulator pressure sensor 348, so that the fluid pressure detected bythe pressure sensor 406 is less influenced by a pressure loss in thehigh pressure passage 356. Accordingly, the pressure sensor 406 permitsa higher degree of detection of the above-indication fluid pressuredifference, in cooperation with the brake cylinder pressure sensor 386,388, than the accumulator pressure sensor 348. By the pressureincreasing control valve 378, it is possible to control the differencebetween the output pressure of the power operated hydraulic pressuresource 314 and the fluid pressure in the wheel brake cylinder 320-323,so that the hydraulic braking pressure in the corresponding wheel brakecylinder can be increased.

Each pressure reducing control valve 380 is connected at its highpressure port 94 to the corresponding wheel brake cylinder 320-323, andat its low pressure port 96 to the reservoir 350 (low pressure passage384). Since the fluid pressure in the reservoir 350 can be considered tobe substantially equal to the atmospheric pressure, the fluid pressuredifference across the control valve 380 can be represented by the fluidpressure as detected by the corresponding brake cylinder pressure sensor386, 388. By controlling the pressure reducing control valve 380, it ispossible to control the difference between the fluid pressures in thewheel brake cylinder 320-323 and the reservoir 350, so that thehydraulic braking pressure in the corresponding wheel brake cylinder canbe reduced.

The fluid passages 334, 336 are provided with respective master cylindercut-off valves 410, 412 and respective master cylinder pressure sensors414, 416. Like the pressure increasing control valves 378 and thepressure reducing valves 380, each master cylinder cut-off valve 410,412 has two ports which are axially spaced apart from each other.However, the valve member of the master cylinder cut-off valve 410, 412is biased by a spring in a direction that causes the valve member to bemoved away from the valve seat.

In the above-indicated arrangement of the master cylinder cut-off valves410, 412, the seating valve is held open maintaining fluid communicationbetween the two ports while no electric current is applied to thesolenoid coil. The seating valve is selectively opened and closed byselective application and removal of an electric current to and from thesolenoid coil, whereby the two ports are selectively communicated withand isolated from each other.

While the fluid pressures in the wheel brake cylinders 320-323 arecontrolled by controlling the pressurized fluid delivered from the poweroperated hydraulic pressure source 314, the master cylinder cut-offvalves 410, 412 are held in the closed state, to isolate the wheel brakecylinders 320-323 from the master cylinder 312. While the mastercylinder cut-off valves 410, 412 and the communication control valves362, 364 are open, the pressurized fluid delivered from the mastercylinder 312 is supplied to all of the wheel brake cylinders 320-323 toactivate respective hydraulic brakes 418.

It will be understood that the pressure increasing control valves 378,pressure reducing control valves 380, communication control valves 362,364, master cylinder cut-off valves 410, 412, brake cylinder pressuresensors 386, 388, master cylinder pressure sensors 414, 416 and pressuresensor 406 are hydraulic pressure control components of the hydraulicbraking pressure control unit 316, which are held by a single holderstructure in the form of a holder block 420 which will be described.

The fluid passage 336 is also provided with a stroke simulator device430, which includes a simulator control valve 432 and a stroke simulator434. The simulator control valve 432 is selectively opened and closed byselective application and removal of an electric current to and from acoil. The simulator control valve 432 is held in the open state whilethe fluid pressures in the wheel brake cylinders 320-323 are controlledby utilizing the pressurized fluid delivered from the power operatedhydraulic pressure source 314, with the master cylinder cut-off valves410, 412 held in the closed state. While the master cylinder cut-offvalves 410, 412 are held open, the simulator control valve 432 is heldin the closed state, to prevent wasting of the pressurized fluiddelivered from the master cylinder 312.

The braking system includes an electronic control device 440(hereinafter abbreviated as “ECU 440”). The ECU 440 is principallyconstituted by a computer incorporating a CPU, a RAM, a ROM and aninput-output portion, as described above with respect to the hydraulicpressure control device 300 provided in the first embodiment. To theinput-output portion, there are connected the accumulator pressuresensor 348, the brake cylinder pressure sensors 386, 388, pressuresensor 406 and master cylinder pressure sensors 414 416, which have beendescribed. To the input-out portion, there are also connected anoperation force sensor 442 arranged to detect an operating force actingon the brake pedal 310, a stroke sensor 444 arranged to detect anoperating stroke of the brake pedal 310, and wheel speed sensors 446arranged to detect the rotating speeds of the front and rear wheels FL,FR, RL, RR. To the input-output portions, there are further connectedthrough respective driver circuits (not shown) the coils of the pumpmotor 342, communication control valves 363, 364, pressure increasingcontrol valves 478, pressure reducing control valves 380 and mastercylinder cut-off valves 410, 412. The various control valves describedabove are controlled to control the hydraulic braking pressures in thewheel brake cylinders 320-323, o the basis of the output signals of thevarious sensors, such as the pressure sensors indicated above.

For instance, the present braking system is controlled such that thedetected actual fluid pressures in the wheel brake cylinders 320-323coincide with a value corresponding to a target vehicle braking force asdesired by the vehicle operator, which target vehicle braking force isobtained on the basis of the output signals of the stroke sensor 444 andthe master cylinder pressure sensors 414, 416. The target vehiclebraking force may be obtained on the basis of the output signals of theoperation force sensor 442 and stroke sensor 444. Where a vehicle drivesystem of the vehicle includes an electric motor, the present brakingsystem may be arranged such that the hydraulic brakes 418 cooperate withthe electric motor to perform a cooperative braking control in which ahydraulic braking force produced by the brakes 418 is controlled suchthat a sum of this hydraulic braking force and a regenerative brakingforce produced by the electric motor coincides with the target vehiclebraking force as desired by the vehicle operator.

Power supply wires and signal wires of the solenoid-operated controlvalves, sensors and other hydraulic pressure control components whichare held by the holder block 420 are connected to the ECU 440 andbatteries, through electrical wiring members such as connectors disposedwithin a box 448 shown in FIG. 20. The ECU 440 may be housed within thebox 448.

In the hydraulic braking pressure control unit 316, the holder block 420is a generally rectangular parallelepiped having six surfaces that aregenerally rectangular, as shown in FIGS. 20 and 21. Namely, the holderblock 420 has a first surface 450 (parallel to an XY plane), in whichthere are formed mounting recesses (which will be described) forattaching the pressure increasing control valves 378, brake cylinderpressure sensors 386 and other hydraulic components. The holder block420 further has a second surface 452 (parallel to an XZ plane), which isadjacent and perpendicular to the first surface 450. In the secondsurface 452, there are formed connecting ports (which will be described)for connection to the various fluid passages (connecting pipes, hoses,etc.) which extend from the master cylinder 312, power operatedhydraulic pressure source 314 and wheel brake cylinders 320-323. Theholder block 420 further has a third surface 454 (parallel to a YZplane), which is adjacent and perpendicular to the first and secondsurfaces 450, 452. In the third surface 454, there is formed aconnecting port (which will be described) for connection to the fluidpassage (pie or hose) which extends from the reservoir 350. The holderblock 420 further has a fourth surface 456 which is parallel andopposite to the first surface 450. The holder block 420 is fixed at thisfourth surface 456 to a suitable member of the vehicle body. The holderblock 420 includes side portions respectively having the first throughfourth surfaces 450, 452, 454, 456.

As shown in FIG. 16, the holder block 420 consists of a front-brakinghalf 457 and a rear-braking half 458 located on the respective oppositesides of a bisector plane which includes a bisector line A and which isperpendicular to the first surface 450 and parallel to the YZ plane. Thebisector line A bisects the X-axis dimension of the holder block 420 andextends in the Y-axis direction. The hydraulic pressure controlcomponents and fluid passages of the hydraulic braking pressure controlunit 316, which are provided for the front wheel brake cylinders 420,421, are attached to and formed within the front-braking half 457, whilethe hydraulic components and fluid passages provided for the rear wheelbrake cylinders 422, 423 are attached to and formed within therear-braking half 458. In the holder block 420, the mounting recessesfor attaching the hydraulic components and the fluid passages for thefront wheel brake cylinders 320, 321 and those for the rear wheel brakecylinders 322, 323 are formed symmetrically with each other, withrespect to the bisector plane which includes the bisector line A andwhich is parallel to the YZ plane.

In the holder block 420, a pressure sensor recess 460 for attaching thepressure sensor 406 is formed in a central portion of the first surface450 through which the bisector line A passes. In a half of the firstsurface 450 which corresponds to the front-braking half 457, there areformed mounting recesses for attaching the hydraulic components for thefront wheel brake cylinders 420, 421, that is: a master cylinder cut-offvalve recess 462 f for attaching the master cylinder cut-off valve 412;a master cylinder pressure sensor recess 464 f for attaching the mastercylinder pressure sensor 416; two pressure increasing valve recesses 466f for attaching the respective two pressure increasing control valves378 for the front left and right wheel brake cylinders 320, 321; twopressure reducing valve recesses 467 f for attaching the respective twopressure reducing control valves 480 for the front left and right wheelbrake cylinders 320, 321; two brake cylinder pressure sensor recesses468 f for attaching the respective two front brake cylinder pressuresensors 386; and a communication-valve recess 470 f for attaching thecommunication control valve 362 for the front wheel brake cylinders 320,321.

In a half of the first surface 450 which corresponds to the rear-brakinghalf 458, there are formed mounting recesses for attaching the hydrauliccomponents for the front wheel brake cylinders 422, 423, that is: amaster cylinder cut-off valve recess 462 r for attaching the mastercylinder cut-off valve 410; a master cylinder pressure sensor recess 464r for attaching the master cylinder pressure sensor 414; two pressureincreasing valve recesses 466 r for attaching the respective twopressure increasing control valves 378 for the rear left and right wheelbrake cylinders 322, 323; two pressure reducing valve recesses 467 r forattaching the respective two pressure reducing control valves 480 forthe rear left and right wheel brake cylinders 322, 323; two brakecylinder pressure sensor recesses 468 r for attaching the respective tworear brake cylinder pressure sensors 386; and a communication-valverecess 470 r for attaching the communication control valve 364 for therear wheel brake cylinders 322, 323.

These mounting recesses 460, 462 f, 462 r, 464 f, 464 r, 466 f-468 f,466 r-468 r, 470 f, 470 r are formed in the first surface 420 parallelto the XY plane, in the Z-axis direction, that is, in a directionsubstantially perpendicular to the XY plane. The appropriate hydraulicpressure control components are attached to the holder block 420 suchthat the axes of the hydraulic components are substantiallyperpendicular to the XY plane (first surface 450), with the end portionsof the hydraulic components projecting from the first surface 450, asshown in FIG. 21.

There will be described positional relationships among the mountingrecesses for the respective hydraulic components. It will be understoodthat the hydraulic components attached at the mounting recesses have thesame positional relationships as those of the mounting recesses.

In the present second embodiment, too, the four pressure increasingvalve recesses 466 f, 466 r are arranged along a straight line B, andthe four pressure reducing valve recesses 467 f, 467 r are arrangedalong a straight line C, while the four brake cylinder pressure sensorrecesses 468 f, 468 r are arranged along a straight line D. Thesestraight lines B, C and D are parallel to the X-axis direction, and arespaced apart from each other in the Y-axis direction by suitabledistances such that the straight line D is almost intermediate betweenthe straight lines B and C. Further, the pressure increasing valverecess 466 f, 466 r, brake cylinder pressure sensor recess 468 f, 468 rand pressure reducing valve recess 467 f, 467 r which are provided foreach of the four wheel brake cylinders 320-323 are arranged along acorresponding one of four straight lines E which are parallel to theY-axis direction and which correspond to the respective four wheel brakecylinders 320-323. Thus, the four pressure increasing valve recesses 466f, 466 r, pressure reducing valve recesses 467 f, 467 r and brakecylinder pressure sensor recesses 468 f, 468 r are arranged in a latticeor grid pattern.

Further, the two master cylinder pressure sensor recesses 464 f, 464 rand one pressure sensor recess 460 are disposed along a straight linebetween the straight lines B and D, while the two communication-valverecesses 470 f, 470 r are disposed between the straight lines D and C.The master cylinder cut-off valve recess 462 f, 462 r, master cylinderpressure sensor recess 464 f, 464 r and communication-valve recess 470f, 170 r which are provided for each of the front and rear pairs ofwheel brake cylinders 320-323 are arranged along a corresponding one oftwo straight lines F which are parallel to the Y-axis direction andwhich correspond to the respective two pairs of wheel brake cylinders320-323.

In the present embodiment, each of the master cylinder pressure sensorrecess 464 f and the master cylinder cut-off valve recess 162 f for thefront wheel brake cylinders 320, 321 is spaced from the two pressureincreasing valve recesses 166 f by a predetermined same distance.Similarly, each of the recesses 464 r, 462 r for the rear wheel brakecylinders 322, 323 is spaced from the two recesses 466 r by apredetermined same distance. Further, the pressure sensor recess 460 isspaced by a predetermined same distance from the intermediate twopressure increasing valve recesses 166 f, 166 r, one of which is for oneof the two front wheel brake cylinders 320, 321 and other of which isfor one of the two rear wheel brake cylinders 322, 323.

As described above, the master cylinder pressure sensor recesses 464 f,464 r and the pressure sensor recess 460 are located on respectivestraight lines which are normal to respective straight segmentsconnecting the adjacent pressure increasing valve recesses 466 f, 466 rand which pass midpoints of the respective straight segments. Thus, thefour pressure increasing valve recesses 466 f, 466 r, the two mastercylinder pressure sensor recesses 464 f, 464 r and the one pressuresensor recess 460 are arranged in a zigzag or staggered pattern.Similarly, the two master cylinder pressure sensor recesses 464 f, 464r, the one pressure sensor recess 460 and the four brake cylinderpressure sensor recesses 468 f, 468 r are arranged in a zigzag orstaggered pattern.

Further, the master cylinder pressure sensor recess 464 f for the frontwheel brake cylinders 320, 321 is located in a substantially centralpart of a rectangle whose four apexes are defined by the two pressureincreasing valve recesses 466 f and two brake cylinder pressure sensorrecesses 468 f for the front wheel brake cylinders 320, 321. Thus, therecess 464 f is spaced from the recesses 466 f and the recesses 468 f,by the same distance.

In addition, the communication-valve recess 470 f for the front wheelbrake cylinders 320, 321 is located on a straight line which is normalto a straight segment connecting the two brake cylinder pressure sensorrecesses 468 f and which passes a midpoint of that straight segment.Namely, the recess 470 f is located on a straight line which is normalto a straight segment connecting the two pressure reducing valverecesses 467 f and which passes a midpoint of that straight segment.

The recesses 464 r, 466 r, 468 r, 467 r for the rear wheel brakecylinders 322, 323 are positioned relative to each other in the samemanner as described above with respect to the recesses 464 f, 466 f, 468f, 467 f.

As described above, the master cylinder cut-off valve recesses 462 andthe master cylinder pressure sensor recesses 464 are disposed on theopposite sides of the straight line B. In this arrangement, the area ofthe first surface 450 of the holder block 420 is more effectively usedthan in an arrangement in which the four recesses 462, 464 are disposedon one side of the straight line B, so that the required size of theholder block 420 can be reduced.

In the second surface 452, there are formed four brake cylinder ports480-483, two master cylinder ports 484, 485 and one pump-device port486, as shown in FIGS. 20 and 21, such that the master cylinder port 484is located between the two adjacent brake cylinder ports 480, 481, andthe master cylinder port 484 is located between the other two adjacentbrake cylinder ports 482, 483, while the pump-device port 486 is locatedbetween the two master cylinder ports 484, 485.

Thus, the brake cylinder ports 480-483, master cylinder ports 484, 485and pump-device port 486 are arranged in a zigzag or staggered pattern,so that the required area of the second surface 452 can be reduced.

In the present arrangement, the front and rear right wheel brakecylinders 321, 323 are connected through hoses or any other connectingmeans to the respective two brake cylinder ports 480, 482, which are theouter ones of the four ports 480-483 located at the ends of the secondsurface 452. Thus, the wheel brake cylinders 321, 323 to be connected tothe master cylinder 412 are connected to the two outer master cylinderports 480, 482. The front and rear left wheel brake cylinders 320, 322are connected through hoses or any other connecting means to therespective two inner brake cylinder ports 481, 483. The master cylinderportion 332 is connected to the master cylinder port 484, while thehydraulic booster portion 330 is connected to the master cylinderportion 485.

In the third surface 454, there is formed a reservoir port 488 connectedto the reservoir 350. The third surface 454, a fifth surface 490opposite to the third surface 454, and a sixth surface 492 opposite tothe second surface 452 have openings 494 which are formed to definefluid passages and which are closed by plugs. Reference numeral 495denotes weight-reducing cutouts provided to reduce the weight of theholder block 420.

The holder block 420 has two master cylinder passages 500, 501 and fourbrake cylinder passages 502-505, which are formed to extend in theY-axis direction. Each of the four brake cylinder passages 502-505consists of a pressure increasing brake cylinder passage 502 a-505 a anda pressure reducing brake cylinder passage 402 b-505 b. The mastercylinder passages 500, 501 are held in communication with the respectivemaster cylinder ports 484, 485, while the pressure increasing brakecylinder passages 502 a-505 a are held in communication with therespective brake cylinder ports 480-483.

The master cylinder passage 500 formed in the front-braking half 457 isformed in communication with the master cylinder cut-off valve recess462 f and the master cylinder pressure sensor recess 464 f. The mastercylinder passage 500 is communicated with an inner port of the mastercylinder cut-off valve 412 attached at the master cylinder cut-off valverecess 464 f. The front-braking half 457 has a connecting passage 506 fformed in communication with an intermediate portion of the mastercylinder cut-off valve 412. The connecting passage 506 f is formed so asto extend in the X-axis direction, and held in communication with thepressure increasing brake cylinder passage 502 a. In the rear-brakinghalf 458, too, the master cylinder passage 501 is communicated with aninner portion of the master cylinder cut-off valve 410 attached at themaster cylinder cut-off valve recess 464 r. The passage 501 is also heldin communication with the master cylinder pressure sensor recess 464 r.The master cylinder passage 501 and the pressure increasing brakecylinder passage 504 a are held in communication with each other througha connecting passage 506 r formed in communication with an intermediateportion of the master cylinder cut-off valve 410.

In the present embodiment, the fluid passage 336 is constituted by themaster cylinder passage 500, connecting passage 506 f, pressureincreasing brake cylinder passage 502 a, etc., while the fluid passage334 is constituted by the master cylinder passage 501, connectingpassage 506 r, pressure increasing brake cylinder passage 504 a, etc.

The pressure increasing brake cylinder passages 502 a-505 a and thecorresponding pressure reducing brake cylinder passages 502 b-505 of thebrake cylinder passages 502-505 are connected to each other through thebrake cylinder pressure sensor recesses 468 f, 468 r. This aspect willbe further described by reference to FIG. 17, with respect to the brakecylinder passage 504 for the rear right wheel brake cylinder 323, by wayof example. The following description is true for the other brakecylinder passages 502, 503 and 505.

The pressure increasing brake cylinder passage 504 a is held incommunication with the pressure increasing valve recess 466 r and thebrake cylinder pressure sensor recess 468 r, while the pressure reducingbrake cylinder passage 504 b is held in communication with the brakecylinder pressure sensor recess 468 r and the pressure reducing valverecess 467 r. The pressure increasing brake cylinder passage 504 a iscommunicated with the intermediate or low pressure port 96 of thepressure increasing control valve 378 attached at the pressureincreasing valve recess 466 r, while the pressure reducing brakecylinder passage 504 b is communicated the inner or high pressure port94 of the pressure reducing control valve 380 attached at the pressurereducing valve recess 467 r. The pressure increasing valve recess 466 rand the pressure reducing vale recess 467 r are formed such that thecorresponding pressure increasing and pressure reducing control valves378, 380 attached at those recesses 466 r, 467 r project from the firstsurface 450 by substantially the same distance.

According to the arrangement of connection of the pressure increasingand pressure reducing brake cylinder passages 504 a, 504 b to therespective pressure increasing and pressure reducing control valves 378,380, the brake cylinder passages 504 a, 504 b must be formed atdifferent positions in the Z-axis direction, namely, at different depthpositions from the first surface 450. Accordingly, a fluid passageextending in the Z-axis direction would be required to connect these twobrake cylinder passages 504 a, 504 b. In the present arrangement inwhich the brake cylinder passages 504 a, 504 b are connected to eachother through the corresponding brake cylinder pressure sensor recess468 r, it is not necessary to form such a fluid passage extending in theZ-axis direction, and it is not necessary to close this fluid passage atits open end. Accordingly, the cost of manufacture of the hydraulicbraking pressure control unit 416 is reduced.

The brake cylinder pressure sensor 488 is connected to the brakecylinder pressure sensor recess 468 r such that a pressure detectingportion of the pressure sensor 488 is located nearer to the firstsurface 450, than the point of connection between the pressureincreasing and pressure reducing brake cylinder passages 504 a, 504 b.The pressure detecting portion is open to a pressure chamber partiallydefined by the pressure sensor recess 468 r, and the two brake cylinderpassages 504 a, 504 b are both held in communication with this pressurechamber. This arrangement permits the brake cylinder pressure sensor 488to detect both of an increase and a decrease of the fluid pressure inthe rear right wheel brake cylinder 323, in the same manner, and istherefore effective to reduce inconsistency between the pressureincrease control and the pressure decrease control.

The holder block 420 has a high pressure passage 510 formed therein soas to extend in the Y-axis direction. The high pressure passage 510 isheld in communication with the pump-device port 486 and the pressuresensor recess 460. The high pressure passage 510 is aligned with thebisector line A as seen in a plane parallel to the first surface 450.

In the present second embodiment described above, the master cylinderpassages 500, 501, brake cylinder passages 502-505 and high pressurepassage 510 are all formed holder block 420, so as to extend in theY-axis direction in parallel with each other. Thus, those passages areorderly arranged so as to effectively reduce the required sizes of theholder block 420 and the hydraulic braking pressure control unit 416.

On the other hand, a single pressure increasing passage 520 is formedcommonly for the four pressure increasing valve recesses 466 f, 466 r,while a single pressure reducing passage 522 is formed commonly for thefour pressure reducing valve recesses 467 f, 467 r. The pressureincreasing passage 520 is formed so as to extend in the X-axis directionand is held in communication with the inner high pressure ports 94 ofthe pressure increasing control valves 378 attached at the pressureincreasing valve recesses 466 f, 466 r. The pressure increasing passage520 is held also in communication with the above-indicated high pressurepassage 510, for communication with the pump device 344. The pressureincreasing passage 520 extends in a direction substantially parallel tothe straight line B indicated above. To the intermediate low pressureports 96 of the pressure increasing control valves 378, there areconnected the wheel brake cylinders 320-323 through the respectivepressure increasing brake cylinder passages 502 a-505 a. In the presentembodiment, the fluid passage 56 is constituted by the high pressurepassage 510, pressure increasing passage 520, brake cylinder passages502 a-505 a, etc. The brake cylinder passages 502 a, 504 a constitutenot only parts of the fluid passages 334, 336 but also a part of thefluid passage 356.

The pressure reducing passage 522 is formed in communication with theintermediate low pressure ports 96 of the pressure reducing controlvalves 380 attached at the pressure reducing valve recesses 467 f, 467r, and is connected to the reservoir port 488. To the reservoir port488, there is connected a reservoir passage 524 communicating with thereservoir 350. To the inner high pressure ports 94 of the pressurereducing control valves 380, there are connected the wheel pressurereducing brake cylinder passages 502 b-505 b communicating with thewheel brake cylinders 320-323. In the present embodiment, the fluidpassage 84 is constituted by the pressure increasing brake cylinderpassages 502 a-505 a, pressure reducing brake cylinder passages 502b-505 b, pressure reducing passage 522, reservoir passage 524, etc.

Since the four pressure increasing valve recesses 466 f, 466 r and thefour pressure reducing valve recesses 467 f, 467 r are arranged alongthe respective straight lines B and C, only one pressure increasingpassage 520 and only one pressure reducing passage 522 are sufficientfor the pressure increasing and pressure reducing control valves 378,380. Accordingly, the number of the required fluid passages can bereduced, making it possible to reduce the cost of manufacture of thehydraulic braking pressure control unit 316. Further, the high pressurepassage 510 and the two master cylinder passages 500, 501 are formed soas to extend respective spacings between the adjacent two pressureincreasing control valves 466 f, 466 r, the required X-axis dimension ofthe holder block 420 can be reduced.

Further, the pressure increasing passage 520 is connected at anintermediate portion thereof to the high pressure passage 510, so thatthe pressurized fluid delivered from the pump device 344 can be utilizedequally for the front wheel brake cylinders 320, 321 and the rear wheelbrake cylinders 322, 323, leading to even distribution of thepressurized fluid. It is noted in particular that the high pressurepassage 510 formed along the bisector line A is effective to reducedeterioration of accuracy of control of the wheel brake cylinderpressures being increased.

It is also noted that the master cylinder passages 500, 501 and the highpressure passage 510 are formed independently of each other. Inaddition, the brake cylinder passages 502 a, 504 a are provided commonlyfor the dynamic system (for operating brakes 418 with the pressurizedfluid delivered from the power operated hydraulic pressure source 314)and the static system (for operating the brakes 418 with the pressurizedfluid delivered from the master cylinder 312), while most of the otherpassages are provided for each of the dynamic and static systems.Further, the wheel brake cylinders 320-323 can be isolated from thepower operated hydraulic pressure source 314 independently of eachother, by the respective pressure increasing control valves 378connected to the respective pressure increasing brake cylinder passages502 a-505 a. This arrangement permits the brakes 418 to be operated bythe static system, even in the event of a failure of the dynamic system.In the event of occurrence of any abnormality such as a fluid leakage inone of the dynamic and static systems, the other system can be operated.Since the master cylinder passages 500, 501 (static system) and the highpressure passage 510 (dynamic system) are formed close to each other, anarrangement for selective operation of the dynamic and static systemscan be made simple. That is, the number of the required components forthe selective operation can be reduced.

On the other hand, the holder block 420 has the connecting passage 358for connecting the two brake cylinder passages 502, 503 for the frontwheel brake cylinders 320, 321, and the connecting passage 360 forconnecting the two brake cylinder passages 504, 505 for the rear wheelbrake cylinders 322, 323, such that those connecting passages 358, 360extend in the X-axis direction.

Described more specifically, the rear wheel-cylinder connecting passage360 includes a first communication passage 530 r and a secondcommunication passage 532 r. As shown in FIGS. 17-19, these first andsecond communication passages 530 r, 532 r are connected to each otherthrough the communication-valve recess 470 r. The first communicationpassage 530 r is formed in communication with an intermediate port ofthe communication control valve 364 attached at the communication valverecess 4704, and with the pressure increasing brake cylinder passage 505a. The second communication passage 532 r is formed in communicationwith an inner port of the communication control valve 364 and with thepressure reducing brake cylinder passage 504 b. Similarly, the frontwheel-cylinder communication passage 348 includes a first communicationpassage 530 f and a second communication passage 532 f for connectingthe two brake cylinder passages 502, 503.

The various hydraulic pressure control components described above areattached to the holder block 420 constructed as described above, asshown in FIG. 21. The positional relationships among the hydrauliccomponents are the same as those among the corresponding mountingrecesses, as indicated previously. The master cylinder cut-off valves412, 414 and other valves as shown in FIG. 21 have not been providedwith the solenoid coils. After those valves are provided with thesolenoid coils, the projecting portions of the valves and pressuresensors are enclosed in a housing 540 placed on the first surface 450 ofthe holder block 420, as shown in FIG. 20. The power supply wires andsignal wire extend out of the housing 540 into the ox 448 in which thelead wires are connected to the appropriate battery and the ECU 440through suitable connecting or wiring members. Since all of thehydraulic pressure control components are attached to the first surface450 of the holder block 420, the lead wires can be easily bundledtogether.

In the illustrated embodiments, the pressure increasing and pressurereducing control valves 84, 86, 378, 380 are linear control valvescapable of continuously controlling a fluid pressure difference on theiropposite sides, by controlling an amount of electric current applied totheir coil. However, these linear control valves may be replaced bysolenoid-operated shut-off valves which are opened and closed byenergization and deenergization of their coil. In this case, the fluidpressure in each wheel brake cylinder can be controlled by controllingthe duty ratio of the corresponding shut-off valve, for example. Whilethe four sets of pressure increasing and pressure reducing controlvalves 84, 86, 378, 380 are provided for the respective four wheel brakecylinders 22, 24, 320-323, a single control valve may be providedcommonly for two or three of the four wheel brake cylinders, or for allof the four wheel brake cylinders.

The holder block 420 may be modified to hold other hydraulic componentssuch as components of the power operated hydraulic pressure source 314(e.g., pump 340, pump motor 342, accumulator 346), components of thestroke simulator device 430, pressure relief valve 352, and reservoir350. Further, it is not essential to provide the four brake cylinderpressure sensors 122, 386, 388 for the respective four wheel brakecylinders, since the fluid pressures in all of the wheel brake cylindersare usually equal to each other during a normal operation of the brakingsystem. While the master cylinder 312 used in the second embodiment isprovided with the hydraulic booster, this mater cylinder 312 may bereplaced by an ordinary master cylinder of tandem type, like the mastercylinder 20 used in the first embodiment. The accumulator pressuresensors 62, 348 may be replaced by an accumulator pressure switch.

In the second embodiment, it is not essential to provide the connectingpassages 358,360 and the communication control valves 362, 364. Theprinciple of the present invention is equally applicable to a hydraulicbraking pressure control unit arranged for use in a braking systemhaving five or more brake cylinders. In the second embodiment, theholder block 420 is attached to the vehicle body at the fourth surface456, the holder block 420 may be attached to the vehicle body, at itsfifth surface 490 or sixth surface 492 which does not have any connectorports. Further, the holder block 420 may be attached to the vehicle bodyat the selected two or more surfaces. The principle of the presentinvention is applicable to a braking system of so-called “diagonal” or“X-crossing” type.

It is to be understood that the present invention may be embodied withvarious other changes, modifications and improvements, such as thosedescribed in the SUMMARY OF THE INVENTION, which may occur to thoseskilled in the art, without departing from the spirit and scope of theinvention defined in the following claims:

1. A hydraulic braking pressure control unit comprising: a plurality ofelectromagnetically operated hydraulic pressure control valves capableof controlling pressure of a working fluid in a plurality of brakecylinders; a power-operated hydraulic pressure source power-operable topressurize the working fluid, and including a pump device having a pumpoperable to pressurize the working fluid received from a low-pressuresource and deliver the pressurized working fluid, and an accumulator forstoring the pressurized working fluid delivered from the pump device; amaster-cylinder pressure sensor operable to detect a pressure of theworking fluid pressurized by a master cylinder; an accumulator pressuresensor operable to detect a pressure of the working fluid stored in saidaccumulator; and a holder structure which holds said plurality ofelectromagnetically operated hydraulic pressure control valves, whereinsaid plurality of electromagnetically hydraulic pressure control valvesinclude four control valves having respective main body portions whichare arranged along a straight line on one surface of said holderstructure and which are four pressure-increasing control valvesconnected to said power-operated hydraulic pressure source and to therespective four brake cylinders or four pressure-reducing control valvesconnected to said low-pressure source and to said respective four brakecylinders, and said holder structure has a delivery passage which isconnected to said power-operated hydraulic pressure source and throughwhich the pressurized working fluid is delivered from said pump device,and at least one master-cylinder passage connected to the mastercylinder manually operable to pressurize the working fluid, each of saidpressure-source passage and said at least one master-cylinder passagebeing formed in said holder structure, so as to extend in a directionintersecting said straight line, between two adjacent ones of saidplurality of control valves, as seen in a plane of said one surface, andfurther wherein said holder structure holds all of said plurality ofelectromagnetically operated hydraulic pressure control valves, saidmaster-cylinder pressure sensor and said accumulator pressure sensorsuch that the main body portions of the electromagnetically operatedhydraulic pressure control valves, master-cylinder pressure sensor andaccumulator pressure sensor are attached to said one surface.
 2. Thehydraulic braking pressure control unit according to claim 1, whereinsaid at least one master-cylinder passage consists of twomaster-cylinder passages each of which is formed so as to extend betweentwo adjacent ones of said plurality of control valves, as seen in saidplane.
 3. A hydraulic braking pressure control unit comprising: apower-operated hydraulic pressure source including a pump device havinga pump operable to pressurize a working fluid received from alow-pressure source and deliver the pressurized working fluid, and anaccumulator for storing the pressurized working fluid delivered from thepump device; a plurality of electromagnetically operated hydraulicpressure control valves capable of controlling pressures of the workingfluid in respective brake cylinders, said plurality ofelectromagnetically operated hydraulic pressure control valves includinga group of respective pressure-increasing control valves connected tosaid power-operated hydraulic pressure source and to the respectivebrake cylinders, and a group of pressure-reducing control valvesconnected to said low-pressure source and to said respective brakecylinders; a master-cylinder pressure sensor operable to detect apressure of the working fluid pressurized by a master cylinder operableby an operator to pressurize the working fluid; an accumulator pressuresensor operable to detect a pressure of the working fluid stored in saidaccumulator; and a holder structure which holds said plurality ofelectromagnetically operated hydraulic pressure control valves such thatmain body portions of said plurality of electromagnetically operatedhydraulic pressure control valves are arranged on one surface of saidholder structure, said plurality of electromagnetically operatedhydraulic control valves including a plurality of control valves themain body portions of which are arranged along a straight line, whereinsaid holder structure having at least one fluid passage which is formedin said holder structure such that each of said at least one fluidpassage extends in a direction intersecting said straight line, betweentwo adjacent ones of said plurality of control valves as seen in a planeof said one surface, said at least one fluid passage including adelivery passage through which said pressurized working fluid isdelivered from said pump device, and wherein said holder structure holdsall of said plurality of electromagnetically operated hydraulic pressurecontrol valves, said master cylinder pressure sensor and saidaccumulator pressure sensor such that the main body portions of theelectromagnetically operated hydraulic pressure control valves, mastercylinder pressure sensor and accumulator pressure sensor are attached tosaid one surface.
 4. A hydraulic braking control unit used for a brakingsystem including a plurality of brake cylinders, a master cylindermanually operable to pressurize a working fluid, and a power-operatedhydraulic pressure source including a pump device having a pump operableto pressurize the working fluid, and an accumulator for storing theworking fluid pressurized by the pump, said hydraulic braking controlunit comprising: a plurality of hydraulic control valves capable ofcontrolling pressure of the working fluid in said plurality of brakecylinders; at least one master-cylinder pressure sensor operable todetect a pressure of the working fluid pressurized by said mastercylinder; an accumulator pressure sensor operable to detect a pressureof the working fluid stored in said accumulator; and a holder structurewhich has at least one master-cylinder passage connecting said mastercylinder to said at least one master-cylinder pressure sensor, and apressure-source passage connecting said accumulator to said accumulatorpressure sensor, and wherein said holder structure holds said pluralityof hydraulic pressure control valves, said at least one master-cylinderpressure sensor and said accumulator pressure sensor such that the mainbody portions of the hydraulic pressure control valves, and main bodyportions of the at least one master-cylinder pressure sensor andaccumulator pressure sensor are attached to one surface of the holderstructure, said pressure-source passage being formed in said holderstructure, so as to extend between two adjacent ones of said pluralityof hydraulic control valves, as seen in a plane of said one surface. 5.A hydraulic braking pressure control unit according to claim 4, whereineach of said at least one master cylinder passage is formed in saidholder structure, so as to extend between two adjacent ones of saidplurality of hydraulic pressure control valves, as seen in a plane ofsaid one surface.